CORROSION of LININGS and COATINGS: Cathodic and Inhibitor Protection and Corrosion Monitoring (Corrosion Engineering Handbook, Second Edition)

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Author: P.E. | Philip A. Schweitzer

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CAT8247—PRELIMS—10/11/2006—21:00—SRIDHAR—XML MODEL B – pp. 1–15




Preface

Corrosion is both costly and dangerous. Billions of dollars are annually spent for the replacement of corroded structures, machinery, and components, including metal roofing, condenser tubes, pipelines, and many other items. In addition to replacement costs are those associated with maintenance to prevent corrosion, inspections, and the upkeep of cathodically protected structures and pipelines. Indirect costs of corrosion result from shutdown, loss of efficiency, and product contamination or loss. Although the actual replacement cost of an item may not be high, the loss of production resulting from the need to shut down an operation to permit the replacement may amount to hundreds of dollars per hour. When a tank or pipeline develops a leak, product is lost. If the leak goes undetected for a period of time, the value of the lost product could be considerable. In addition, contamination can result from the leaking material, requiring cleanup, and this can be quite expensive. When corrosion takes place, corrosion products build up, resulting in reduced flow in pipelines and reduced efficiency of heat transfer in heat exchangers. Both conditions increase operating costs. Corrosion products may also be detrimental to the quality of the product being handled, making it necessary to discard valuable materials. Premature failure of bridges or structures because of corrosion can also result in human injury or even loss of life. Failures of operating equipment resulting from corrosion can have the same disastrous results. When all of these factors are considered, it becomes obvious why the potential problem of corrosion should be considered during the early design stages of any project and why it is necessary to constantly monitor the integrity of structures, bridges, machinery, and equipment to prevent premature failures. To cope with the potential problems of corrosion, it is necessary to understand 1. Mechanisms of corrosion 2. Corrosion resistant properties of various materials 3. Proper fabrication and installation techniques 4. Methods to prevent or control corrosion 5. Corrosion testing techniques 6. Corrosion monitoring techniques Corrosion is not only limited to metalic materials but also to all materials of construction. Consequently, this handbook covers not only metallic materials but also all materials of construction.


Chapter 1 provides information on mortars, grouts, and monolithic surfacings. Chapter 2 and Chapter 3 explain means of controlling/preventing corrosion through the use of inhibitors or cathodic protection. In many instances, it is more economical to construct a tank or processing vessel of a less expensive metal, such as carbon steel, rather than an expensive alloy and install a lining to provide protection from corrosion. Chapter 4 through Chapter 6 provides details of various lining materials of both sheet and liquid form, while Chapter 7 through Chapter 10 provides details of coating materials, both organic and metallic. Compatibility charts are provided in all cases. Because processing conditions can change or upsets take place, it is necessary that any corrosion that may occur be monitored. Chapter 11 discusses various techniques that may be employed to keep check on any corrosion that may be taking place internally in a vessel or pipeline. It is the intention of this book that regardless of what is being built, whether it is a bridge, tower, pipeline, storage tank, or processing vessel, information for the designer/engineer/maintenance personnel/or whoever is responsible for the selection of material of construction will be found in this book to enable them to avoid unnecessary loss of material through corrosion. Philip A. Schweitzer


Author

Philip A. Schweitzer is a consultant in corrosion prevention, materials of construction, and chemical engineering based in York, Pennsylvania. A former contract manager and material specialist for Chem-Pro Corporation, Fairfield, New Jersey, he is the editor of the Corrosion Engineering Handbook and the Corrosion and Corrosion Protection Handbook, Second Edition; and the author of Corrosion Resistance Tables, Fifth Edition; Encyclopedia of Corrosion Technology, Second Edition; Metallic Materials; Corrosion Resistant Linings and Coatings; Atmospheric Degradation and Corrosion Control; What Every Engineer Should Know About Corrosion; Corrosion Resistance of Elastomers; Corrosion Resistant Piping Systems; Mechanical and Corrosion Resistant Properties of Plastics and Elastomers (all titles Marcel Dekker, Inc.), and Paint and Coatings, Applications and Corrosion Resistance (Taylor & Francis). Schweitzer received the BChE degree (1950) from Polytechnic University (formerly Polytechnic Institute of Brooklyn), Brooklyn, New York.


Contents

Chapter 1 1.1 1.2 1.3

1.4

Chemical Resistant Mortars, Grouts, and Monolithic Surfacings ........................................................................................ 1 Introduction .................................................................................................. 1 Materials Selection....................................................................................... 3 Chemical-Resistant Mortars and Grouts.................................................. 3 1.3.1 Organic ............................................................................................. 4 1.3.1.1 Epoxy .................................................................................. 4 1.3.1.2 Furans ................................................................................. 7 1.3.1.3 Phenolics............................................................................. 9 1.3.1.4 Polyesters ......................................................................... 10 1.3.1.5 Vinyl Ester and Vinyl Ester Novolac........................... 12 1.3.2 Inorganic......................................................................................... 13 1.3.2.1 Sulfur................................................................................. 14 1.3.2.2 Silicates ............................................................................. 15 Chemical-Resistant Monolithic Surfacings and Polymer Concretes ..................................................................................................... 16 1.4.1 Chemical Resistance ..................................................................... 37 1.4.2 Applications................................................................................... 40

Chapter 2 Cathodic Protection ..................................................................... 2.1 Introduction ................................................................................................ 2.2 Background ................................................................................................. 2.3 Theory.......................................................................................................... 2.4 Method of Application.............................................................................. 2.4.1 Impressed Current Systems ........................................................ 2.4.1.1 Current Requirements.................................................... 2.4.2 Sacrificial Anodes ......................................................................... 2.4.2.1 Anode Requirements...................................................... 2.4.2.2 Anode Materials and Backfill ....................................... 2.5 Use with Coatings...................................................................................... 2.6 Testing for Completeness of Protection ................................................. 2.6.1 Coupon Tests ................................................................................. 2.6.2 Colormetric Tests .......................................................................... 2.6.3 Potential Measurements .............................................................. 2.7 Overprotection............................................................................................ 2.8 Economics ...................................................................................................

43 43 43 44 46 46 47 47 48 50 51 52 52 52 52 53 53

Chapter 3 Corrosion Inhibitors.................................................................... 55 3.1 Introduction ................................................................................................ 55


3.2 3.3

Inhibitor Evaluation .................................................................................. Classification of Inhibitors........................................................................ 3.3.1 Passivation Inhibitors................................................................... 3.3.2 Organic Inhibitors......................................................................... 3.3.3 Precipitation Inhibitors ................................................................ 3.4 Inhibition of Acid Solution....................................................................... 3.4.1 Physical Adsorption ..................................................................... 3.4.2 Chemisorption ............................................................................... 3.4.3 Interactions between Adsorbed Inhibitors ............................... 3.4.4 Relationships between Inhibitor Reactivity and Efficiency ................................................................................ 3.5 Inhibition of Near Neutral Solutions...................................................... 3.6 Inhibition of Alkaline Solutions .............................................................. 3.7 Temporary Protection with Inhibitors .................................................... 3.8 Inhibition of Localized Corrosion ........................................................... 3.9 Summary ..................................................................................................... References ............................................................................................................

57 57 57 58 59 59 60 61 62 62 63 64 65 65 66 67

Chapter 4 Liquid-Applied Linings ............................................................. 69 4.1 Design of the Vessel................................................................................... 69 4.2 Vessel Preparation...................................................................................... 74 4.3 Lining Function .......................................................................................... 75 4.4 Lining Selection.......................................................................................... 75 4.5 Lining Application..................................................................................... 80 4.6 Inspection .................................................................................................... 81 4.7 Curing .......................................................................................................... 82 4.8 Safety during Application ........................................................................ 82 4.9 Causes of Lining Failure........................................................................... 83 4.10 Specific Liquid Linings............................................................................. 84 4.10.1 Phenolics....................................................................................... 84 4.10.2 Epoxy ............................................................................................ 85 4.10.3 Furans ........................................................................................... 88 4.10.4 Vinyl Esters .................................................................................. 93 4.10.5 Epoxy Polyamide ........................................................................ 93 4.10.6 Coal Tar Epoxy ............................................................................ 97 4.10.7 Coal Tar ........................................................................................ 97 4.10.8 Urethanes ................................................................................... 103 4.10.9 Neoprene .................................................................................... 107 4.10.10 Polysulfide Rubber.................................................................... 110 4.10.11 Hypalon....................................................................................... 110 4.10.12 Plastisols...................................................................................... 116 4.10.13 Perfluoroalkoxy......................................................................... 121 4.10.14 Fluorinated Ethylene Propylene ............................................ 121 4.10.15 PTFE (Teflon)............................................................................. 125 4.10.16 Tefzel........................................................................................... 134


4.10.17 Halar ........................................................................................... 4.10.18 Fluoroelastomers ...................................................................... 4.10.19 Polyvinylidene Fluoride .......................................................... 4.10.20 Isophthalic Polyester................................................................ 4.10.21 Bisphenol-A Fumurate Polyesters ......................................... 4.10.22 Halogenated Polyesters ........................................................... 4.10.23 Silicones...................................................................................... References ..........................................................................................................

134 142 147 147 159 164 171 174

Chapter 5 Comparative Resistance of Organic Linings........................ 175 Reference ............................................................................................................ 286 Chapter 6 Sheet Linings .............................................................................. 6.1 A Shell Design .......................................................................................... 6.2 Considerations in Liner Selection ......................................................... 6.3 Design Considerations ............................................................................ 6.3.1 Permeation ................................................................................... 6.3.2 Absorption ................................................................................... 6.3.3 Environmental Stress Cracking ................................................ 6.4 Causes of Lining Failure......................................................................... 6.4.1 Liner Selection ............................................................................. 6.4.2 Inadequate Surface Preparation ............................................... 6.4.3 Thermal Stresses ......................................................................... 6.4.4 Permeation ................................................................................... 6.4.5 Absorption ................................................................................... 6.4.6 Welding Flaws ............................................................................. 6.4.7 Debonding.................................................................................... 6.4.8 Operation...................................................................................... 6.5 Elastomeric Linings ................................................................................. 6.5.1 Natural Rubber............................................................................ 6.5.1.1 Soft Natural Rubber Linings ....................................... 6.5.1.2 Multiply Natural Rubber Linings .............................. 6.5.1.3 Semihard Natural Rubber Linings............................. 6.5.1.4 Hard Natural Rubber Linings .................................... 6.5.2 Isoprene ........................................................................................ 6.5.3 Neoprene ...................................................................................... 6.5.4 Butyl Rubber................................................................................ 6.5.5 Chlorosulfonated Polyethylene (Hypalon)............................. 6.5.6 Urethane Rubbers ....................................................................... 6.5.7 Polyester Elastomer .................................................................... 6.5.8 Chlorobutyl Rubber.................................................................... 6.5.9 Ethylene Propylene Rubber ...................................................... 6.5.10 Nitrile Rubber (NBR, Buna-N)................................................. 6.5.11 Fluoroelastomers......................................................................... 6.6 Thermoplastic Linings ............................................................................


287 287 288 290 290 292 293 293 294 294 294 294 294 294 294 295 295 296 296 300 300 306 306 309 310 314 318 322 325 328 336 336 343

6.6.1 Polyvinyl Chloride...................................................................... 6.6.2 Chlorinated Polyvinyl Chloride ............................................... 6.6.3 Polyvinylidene Fluoride ............................................................ 6.6.4 Polypropylene ............................................................................. 6.6.5 Polyethylene ................................................................................ 6.6.6 Tetrafluoroethylene..................................................................... 6.6.7 Fluorinated Ethylene Propylene............................................... 6.6.8 Perfluoralkoxy ............................................................................. 6.6.9 Ethylene Tetrafluoroethylene .................................................... 6.6.10 Chlorotrifluoroethylene ............................................................. 6.6.11 Polyvinylidene Chloride (Saran).............................................. Reference ............................................................................................................

345 345 345 353 362 367 367 385 386 386 398 402

Chapter 7 Coatings ....................................................................................... 7.1 Introduction to Coatings......................................................................... 7.1.1 Principles of Corrosion Protection ........................................... 7.1.2 Corrosion Cell.............................................................................. 7.1.3 EMF Control Protection .............................................................. 7.1.4 Cathodic Control Protection ..................................................... 7.1.4.1 Galvanic Action of Coating Layer ............................. 7.1.5 Anodic Control Protection ........................................................ 7.1.5.1 Single Layer Coatings .................................................. 7.1.5.2 Multilayer Coatings ...................................................... 7.1.6 Resistance Control Protection ................................................... 7.2 Metallic Coatings ..................................................................................... 7.2.1 Methods of Producing Coatings............................................... 7.2.1.1 Electroplating................................................................. 7.2.1.2 Electroless Plating ......................................................... 7.2.1.3 Electrophoretic Deposition .......................................... 7.2.1.4 Cathodic Sputtering...................................................... 7.2.1.5 Diffusion Coating.......................................................... 7.2.1.6 Flame Spraying ............................................................. 7.2.1.7 Plasma Spraying ........................................................... 7.2.1.8 Hot Dipping................................................................... 7.2.1.9 Vacuum and Vapor Deposition .................................. 7.2.1.10 Gas Plating..................................................................... 7.2.1.11 Fusion Bonding ............................................................. 7.2.1.12 Explosion Bonding ....................................................... 7.2.1.13 Metal Cladding ............................................................. 7.3 Noble Coatings......................................................................................... 7.3.1 Nickel Coatings ........................................................................... 7.3.2 Satin-Finish Nickel Coating ...................................................... 7.3.3 Nickel–Iron Alloy Coating ........................................................ 7.3.4 Chromium Coatings ................................................................... 7.3.5 Tin Coatings (Tinplate) ..............................................................

403 403 403 405 411 412 413 414 414 415 416 417 417 417 418 418 419 420 420 420 420 420 421 421 421 421 421 423 426 426 427 429


7.4

7.5 7.6 7.7 7.8 7.9 7.10 7.11 7.12

7.13

7.3.6 Lead Coatings.............................................................................. 7.3.7 Terneplate..................................................................................... 7.3.8 Gold Coatings.............................................................................. 7.3.9 Copper Coatings ......................................................................... Nonnoble Coatings .................................................................................. 7.4.1 Zinc Coatings............................................................................... 7.4.1.1 Hot Dipping................................................................... 7.4.1.2 Zinc Electroplating ....................................................... 7.4.1.3 Mechanical Coating ...................................................... 7.4.1.4 Sherardizing................................................................... 7.4.1.5 Thermally Sprayed Coatings ...................................... 7.4.1.6 Zinc Dust Painting........................................................ 7.4.1.7 Corrosion of Zinc Coatings ......................................... Zinc–5% Aluminum Hot-Dip Coatings ............................................... Zinc–55% Aluminum Hot-Dip Coatings ............................................. Zinc–15% Aluminum Thermal Spray................................................... Zinc–Iron Alloy Coatings ....................................................................... Aluminum Coatings ................................................................................ Cadmium Coatings ................................................................................. Manganese Coatings ............................................................................... Conversion Coatings............................................................................... 7.12.1 Phosphate Coating.................................................................... 7.12.2 Chromate Coating..................................................................... 7.12.3 Oxide Coatings.......................................................................... 7.12.4 Anodized Coatings ................................................................... Organic Coatings ..................................................................................... 7.13.1 Composition of Organic Coatings.......................................... 7.13.1.1 Resin Component ..................................................... 7.13.1.2 Pigments..................................................................... 7.13.1.3 Fillers (Extenders)..................................................... 7.13.1.4 Additives.................................................................... 7.13.1.5 Solvents ...................................................................... 7.13.2 Surface Preparation .................................................................. 7.13.3 Application Methods................................................................ 7.13.3.1 Brushing ..................................................................... 7.13.3.2 Spray........................................................................... 7.13.3.3 Roller Coating ........................................................... 7.13.3.4 Powder Coating ........................................................ 7.13.3.5 Electrodeposition ...................................................... 7.13.3.6 Multilayer Coatings.................................................. 7.13.4 Factors Affecting Life of Film ................................................. 7.13.5 Strength of Paint Film .............................................................. 7.13.6 Adhesion of Paint Film ............................................................ 7.13.7 Types of Corrosion under Organic Coatings ....................... 7.13.7.1 Cathodic Delamination............................................ 7.13.7.2 Anodic Undermining...............................................


431 432 432 433 435 440 440 441 442 442 442 443 443 448 448 451 451 452 452 452 453 454 455 457 457 459 461 461 467 468 469 469 469 471 472 472 473 473 473 475 475 476 477 479 480 480

7.13.7.3 Filiform Corrosion .................................................... 7.13.8 Causes of Coating Failures...................................................... 7.13.9 Maintenance of the Coating .................................................... References ..........................................................................................................

481 482 484 485

Chapter 8 Specific Organic Coatings ........................................................ 8.1 Thermoplastic Resins .............................................................................. 8.1.1 Vinyls ............................................................................................ 8.1.2 Chlorinated Rubber .................................................................... 8.1.3 Acrylics ......................................................................................... 8.2 Thermosetting Resins .............................................................................. 8.2.1 Epoxy ............................................................................................ 8.2.2 Polyamine Epoxy ........................................................................ 8.2.3 Polyamide Epoxy ........................................................................ 8.2.4 Aliphatic Polyamine ................................................................... 8.2.5 Esters of Epoxies and Fatty Acids ........................................... 8.2.6 Coal Tar Plus Epoxy ................................................................... 8.2.7 Urethanes ..................................................................................... 8.2.8 Polyesters ..................................................................................... 8.2.9 Vinyl Esters .................................................................................. 8.3 Autooxidative Cross-Linking Paints..................................................... 8.3.1 Epoxy Esters ................................................................................ 8.3.2 Alkyd Resin ................................................................................. 8.3.3 Oil-Based Paints .......................................................................... 8.3.4 Water Emulsion Paints............................................................... 8.3.5 Silicones ........................................................................................ 8.4 Bituminous Paints.................................................................................... 8.4.1 Asphalt Paint ............................................................................... 8.4.2 Coal Tar ........................................................................................ 8.5 Zinc-Rich Paints ....................................................................................... 8.6 Selecting a Paint System ......................................................................... 8.6.1 Area 1. Mild Exposure ............................................................... 8.6.2 Area 2. Temporary Protection; Normally Dry Interiors ....... 8.6.3 Area 3. Normally Dry Exteriors ............................................... 8.6.4 Area 4. Freshwater Exposure.................................................... 8.6.5 Area 5. Saltwater Exposure ....................................................... 8.6.6 Area 6. Freshwater Immersion ................................................. 8.6.7 Area 7. Saltwater Immersion .................................................... 8.6.8 Area 8. Acidic Chemical Exposure (pH 2.0–5.0) ................... 8.6.9 Area 9. Neutral Chemical Exposure (pH 5.0–10.0) ............... 8.6.10 Area 10. Exposure to Mild Solvents ........................................ 8.6.11 Area 11. Extreme pH Exposure ................................................

487 487 487 488 488 489 490 490 490 490 490 491 491 492 492 492 493 493 494 494 494 495 495 495 495 496 499 499 503 503 505 506 506 506 506 507 507

Chapter 9 Cementitious Coatings.............................................................. 509 9.1 Silicates ...................................................................................................... 510


9.2 9.3

Calcium Aluminate ................................................................................. 512 Portland Cement ...................................................................................... 512

Chapter 10 Coatings for Concrete.............................................................. 10.1 Surface Preparation ............................................................................... 10.1.1 Surface Cleaning...................................................................... 10.1.2 Surface Abrading..................................................................... 10.1.3 Acid Etching............................................................................. 10.2 Coating Selection ................................................................................... 10.3 Installation of Coatings ......................................................................... 10.4 Epoxy and Epoxy Novolac Coatings.................................................. 10.5 Polyester Coatings ................................................................................. 10.5.1 Vinyl Ester/Vinyl Ester Novolac Coatings ......................... 10.6 Acrylic Coating ...................................................................................... 10.7 Urethane Coatings ................................................................................. 10.8 Phenolic/Epoxy Novolac Coatings .................................................... References ..........................................................................................................

515 516 516 518 518 518 519 521 524 526 527 528 530 532

Chapter 11 Corrosion Monitoring ............................................................. 11.1 Measuring and Monitoring Corrosion ............................................... 11.1.1 Radiography ............................................................................. 11.1.2 Ultrasonic Measurement ........................................................ 11.1.3 Visual Inspection ..................................................................... 11.1.4 Destructive Analysis ............................................................... 11.1.5 Chemical Analysis................................................................... 11.1.6 Coupons .................................................................................... 11.1.7 Hydrogen Probes..................................................................... 11.1.8 Polarization Studies ................................................................ 11.1.9 Electrical Impedance Spectroscopy ...................................... 11.1.10 Electrochemical Noise ............................................................ 11.1.11 Electrical Resistance ................................................................ 11.1.12 CORROSOMETERw Systems ................................................ 11.1.13 Linear Polarization Resistance .............................................. 11.1.14 CORRATERw Systems............................................................ 11.2 Comparison of CORROSOMETER (ER) and CORRATER (LPR) Measurement Techniques ..................................................................... 11.3 Applications Suited to CORRATER (LPR) and CORROSOMETER (ER) Techniques ...................................................

533 534 534 534 535 535 535 536 537 537 538 539 539 539 541 542 545 546

Index ................................................................................................................... 549


1 Chemical Resistant Mortars, Grouts, and Monolithic Surfacings

1.1 Introduction The industrialization of America following the turn of the century and the subsequent expansion of our agricultural industry created the need for chemical-resistant construction materials. The steel and metalworking, chemical (including explosives), dyestuffs, and fertilizer industries were the initial industries with severe corrosion problems. The pulp and paper, petroleum, petrochemical, and automotive industries followed with similar corrosion problems. Specifically, the pickling, plating, and galvanizing of metals requires sulfuric, hydrochloric, hydrofluoric, chromic, nitric, and phosphoric acids. The manufacture of explosives, dyestuffs, fertilizer, and other agricultural products requires the same acids as well as other corrosive chemicals. The pulp and paper industry, from inception of the wood chip into the digester and the subsequent bleaching of pulp, required similar acids. Sodium hydroxide, sodium hypochlorite, and chlorine were additional mandated chemicals for this and other industries. Rail, automotive, petroleum, and petrochemical operations, and food and beverage sanitation mandates ultimately contributed to additional industrial corrosion problems. Early reaction vessels in the process industries utilized lead linings with or without further protection from various types of brick, tile, porcelain, and ceramic sheathings. The early jointing materials for installing these ceramictype linings utilized siliceous fillers mixed with inorganic binders based on various silicates, as well as mortar based on litharge and glycerine. The limitations of these mortars and grouts stimulated research for better setting and jointing materials for installing chemical-resistant brick, tile, and ceramics. The best brick or tile in the world for installing floors or tank linings is only as good as the mortars and grouts used to install it. 1

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Corrosion of Linings and Coatings

In the early 1930s, the first plasticized hot-pour, acid-resistant sulfur mortar was introduced in the United States. Sulfur mortars were immediately accepted by industry; however, they have thermal limitations and lack resistance to alkalies and solvents. In the late 1930s, the first American acid-, salt-, and solvent-resistant phenolic mortar was introduced. In the early 1940s, the first furan mortar was developed and introduced in the United States and soon became the standard of the industry. It provided outstanding resistance to acids, alkalies, salts, and solvents. Additional resin-binder systems have been developed for use as chemicalresistant mortars, grouts, and monolithic surfacings. It is important to understand the vernacular of an industry. “Mortar” and “grout” are terms generally associated with the brick, tile, and masonry trades. Mortars and grouts are used for “setting” and joining various types and sizes of brick and tile. A mortar can be described as a material of heavy consistency that can support the weight of the brick or tile without being squeezed from the joints while the joint is curing. Chemical-resistant mortar joints are customarily approximately 1/8 in. (3 mm) wide. A mortar is applied by buttering each unit and is generally associated with bricklayer trade. A grout can be described as a thin or “soupy” mortar used for filling joints between previously laid brick or tile. Grout joints are customarily approximately 1/4 in. (6 mm) wide. A grout is applied by “squeegeeing” it into the open joints with a flat, rectangular, rubber-faced trowel and is generally associated with tilesetting. Chemical-resistant machinery grouts are also available whose formulations are similar to those of the tile grouts. Machinery grouts generally utilize larger aggregates than tile grouts. Resin viscosities can also vary from those of the tile grouts. Chemical-resistant monolithic surfacings or toppings are a mixture of a liquid synthetic resin binder, selected fillers, and a setting agent for application to concrete in thicknesses ranging from approximately 1/16 in. (1.5 mm) to 1/2 in. (13 mm). Materials applied in thicknesses greater than 1/2 in. (13 mm) are usually described as polymer concretes. Polymer concretes are defined as a composition of low-viscosity binders and properly graded inert aggregates that when combined and thoroughly mixed, yield a chemicalresistant synthetic concrete that can be precast or poured in place. Polymer concretes can also be used as a concrete surfacing, with the exception of sulfur cement polymer concrete. All polymer concretes can be used for total poured-in-place reinforced or unreinforced slabs. They can also be used for precasting of slabs, pump pads, column bases, trenches, tanks, and sumps, to mention a few. By definition, monolithic surfacings are also polymer concretes. Chemical-resistant mortars, grouts, and monolithic surfacings are based on organic and inorganic chemistry. The more popular materials of each group will be discussed.


Chemical Resistant Mortars, Grouts, and Monolithic Surfacings

3

1.2 Materials Selection The success or failure of a chemical-resistant mortar, grout, or monolithic surfacing is based on proper selection of materials and their application. To select the proper material, the problem must first be defined: 1. Identify all chemicals that will be present and their concentration. It is not enough to say that pH will be 4, 7, or 11. This determines if it is acid, neutral, or alkaline; it does not identify whether the environment is oxidizing or nonoxidizing, organic or inorganic, alternately acid or alkaline, etc. 2. Is the application fumes and splash or total immersion? Floors can have integral trenches and sumps, curbs, pump pads. 3. What are the minimum or maximum temperatures to which the installation will be subjected? 4. Is the installation indoors or outdoors? Thermal shock and ultraviolet exposure can be deleterious to many resin systems. 5. What are the physical impositions? Foot traffic vs. vehicular traffic, impact from dropping steel plates vs. paper boxes, etc., must be defined. 6. Longevity—how long must it last? Is process obsolescence imminent? This could have a profound effect on cost. 7. Must it satisfy standards organizations such as USDA or FDA? Some systems do not comply. 8. Are the resin systems odoriferous? This could preclude their use in many processing plants such as food, beverage, and pharmaceutical. Many systems are odoriferous. Answers to these questions will provide the necessary information to make a proper selection from the available resin system.

1.3 Chemical-Resistant Mortars and Grouts Chemical-resistant mortars and grouts are composed of a liquid resin or an inorganic binder, fillers such as carbon, silica, and combinations thereof, and a hardener or catalyst system that can be incorporated in the filler or added as a separate component. The workability of a mortar or grout is predicated on properly selected fillers or combinations of fillers, particle size and gradation of these fillers, resin viscosity, and reactivity of catalysts and hardeners. Improper filler gradation and high-viscosity resins produce mortars with poor working


4

Corrosion of Linings and Coatings TABLE 1.1 Guide to Chemical Resistance of Fillers Filler Medium, 20%

Carbon

Silica

Combination Carbon–Silica

Hydrochloric acid Hydrofluoric acid Sulfuric acid Potassium hydroxide Sodium hydroxide Neutral salts Solvents, conc.

R R R R R R R

R N R N N R R

R N R N N R R

R, recommended; N, not recommended.

properties. Hardener systems must be properly balanced for application at thermal ranges of approximately 60–908F (15–328C). The higher the temperature, the faster the set; the lower the temperature, the slower the set. Improper ambient and material temperature can also have a deleterious effect on the quality of the final installation, i.e., adhesion to brick, tile or substrate, high or low, rough or porous, or improperly cured joints. The most popular fillers used are carbon, silica, and combinations thereof. Baraytes has been used in conjunction with carbon and silica for specific end-use application. Irrefutably, carbon is the most inert of the fillers; consequently, in many of the resin and sulfur systems, it is the filler of choice. It provides resistance to most chemicals, including strong alkalies, hydrofluoric acid, and other fluorine chemicals. The general chemical resistance of various fillers to acids, alkalies, salts, fluorine chemicals, and solvents is enumerated in Table 1.1. The most popular resin systems from which chemical-resistant mortars and grouts are formulated follow. 1.3.1 Organic 1.3.1.1 Epoxy The most popular epoxy resins used in the formulation of corrosion-resistant mortars, grout, and monolithic surfacings are low-viscosity liquid resins based on 1. Bisphenol A 2. Bisphenol F (epoxy Novolac) 3. Epoxy phenol Novolac



5

These base components are reacted with epichlorohydrin to form resins of varying viscosity and molecular weight. The subsequent molecular orientation is predicated on the hardener systems employed to effect the cure or solidification of the resin. The hardening systems selected will dictate the following properties of the cured system: 1. Chemical and thermal resistance 2. Physical properties 3. Moisture tolerance 4. Workability 5. Safety during use Of the three systems enumerated, the bisphenol A epoxy has been the most popular followed by the bisphenol F, sometimes referred to as an epoxy Novolac resin. The epoxy phenol Novolac is a higher viscosity resin that requires various types of diluents or resin blends for formulating mortars, grouts, and some monolithic surfacings. The bisphenol A resin uses the following types of hardeners: 1. Aliphatic amines 2. Modified aliphatic amines 3. Aromatic amines 4. Others Table 1.2 shows effects of the hardener on the chemical resistance of the finished mortar or grout of bisphenol A systems when exposed to organic, inorganic, and oxidizing acids as well as aromatic solvents. Table 1.3 provides, summary chemical resistance of optimum chemicalresistant bisphenol A, and aromatic amine cured with bisphenol F resin systems. TABLE 1.2 Types of Epoxy Hardeners and Their Effects on Chemical Resistance Hardeners Medium

Aliphatic Amines

Modified Aliphatic Amines

Aromatic Amines

Acetic acid, 5–10% Benzene Chromic acid, !5% Sulfuric acid, 25% Sulfuric acid, 50% Sulfuric acid, 75%

C N C R C N

N N N C N N

R R R R R R

R, recommended; N, not recommended; C, conditional.


6


TABLE 1.3 General Corrosion Resistance of Epoxy Mortars Hardenersa Aromatic Amines Bisphenol

Corrodent at Room Temperature

Aliphatic Amines


A

F

Acetic acid 5–10% Acetone Benzene Butyl acetate Butyl alcohol Chromic acid 5% Chromic acid 10% Formaldehyde 35% Gasoline Hydrochloric acid to 36% Nitric acid 30% Phosphoric acid 50% Sulfuric acid 25% Sulfuric acid 50% Sulfuric acid 75% Trichloroethylene

C U U U R U U R R U U U R U U U

U U U U R U U R R U U U U U U U

R U R U R R U R R R U R R R U U

U R R R R R R R R U R R R U R

a

R, recommended; U, unsatisfactory.

Amine hardening systems, being alkaline, provide a high degree of compatibility of these systems for application to a multitude of substrates such as poured-in-place and precast concrete, steel, wood, fiberglassreinforced plastics (FRP), brick, tile, ceramics, etc. The most popular filler used for epoxy mortars and grouts is silica. Unfortunately, this precludes their use in hydrofluoric acid, other fluorine chemicals, and hot, strong alkalies. Carbon-filled mortars and grouts are available, however, with some sacrifice to working properties. Fortunately, their most popular applications have been industrial and institutional whereby optimum physical properties are required and exposure to elevated temperatures and corrosives are moderate. Epoxy systems have outstanding physical properties. They are the premier products where optimum adhesion is a service requirement. Amine hardening systems are the most popular for ambient-temperaturecuring epoxy mortars, grouts, and monolithic surfacings. These systems are hygroscopic, and they can present allergenic responses to sensitive skin. These responses can be minimized, or virtually eliminated, by attention to personal hygiene and the use of protective creams on exposed areas of skin, i.e., face, neck, arms, and hands. Protective garments, including gloves, are recommended when using epoxy materials.



7

The bisphenol F or epoxy Novolac are similar systems to the bisphenol A epoxy systems in that they use alkaline hardeners and the same fillers. The major advantage for the use of the bisphenol F is improved resistance to 1. Aliphatic and aromatic solvents 2. Higher concentrations of oxidizing and nonoxidizing acids Disadvantages of these systems are that they involve 1. Less plastic with slightly more shrinkage 2. Slightly less resistance to alkaline mediums The thermal resistance and physical properties are otherwise very similar to the bisphenol A systems. 1.3.1.2 Furans The polyfurfuryl alcohol or furan resins are the most versatile of all the resins used to formulate corrosion-resistant mortars and grouts. They are used for monolithic surfacings; however, they are not a popular choice because of their brittleness and their propensity to shrink. They provide a broad range of chemical resistance to most nonoxidizing organic and inorganic acids, alkalies, salts, oils, greases, and solvents to temperatures of 3608F (1828C). Table 1.4 provides comparative chemical resistance for furan resin mortars and grouts with 100% carbon and part carbon/ silica fillers. Of all the room temperature curing resins, furans are one of the highest in thermal resistance with excellent physical properties. Furan resins are unique in that they are agriculturally, not petrochemically, based as are most synthetic resins. Furfuryl alcohol is produced from such agricultural by-products as corn cob, bagasse, rice, and oat hull. The furan resin mortars and grouts are convenient-to-use, twocomponent systems consisting of the resin and a filler. The catalyst or hardener system is an acid that is contained in the filler. The most popular fillers are carbon, silica, and a combination of carbon and silica. The 100% carbon-filled furan resin mortars and grouts provide the broadest range of chemical resistance because of the inherent chemical resistance of the resin and the carbon filler to all concentrations of all alkalies, as well as to hydrofluoric acid and other fluorine chemicals. The advantages of mortars with part carbon and part silica fillers are slightly improved workability, physical properties, and cost. Grouts generally utilize 100% carbon filler because of the superior chemical resistance and flow properties. The acidic catalysts employed in furan systems preclude their use directly on concrete, steel, and other substrates that could react with the acid.


8

Corrosion of Linings and Coatings TABLE 1.4 Chemical Resistance Furan Resins Mortars and Grouts: 100% Carbon vs. Part Carbon/Silica Fillers Medium, RT

100% Carbon

Part Carbon/Silica

Acetic acid, glacial Benzene Cadmium salts Chlorine dioxide Chromic acid Copper salts Ethyl acetate Ethyl alcohol Formaldehyde Fatty acids Gasoline Hydrochloric acid Hydrofluoric acid Iron salts Lactic acid Methyl ethyl ketone Nitric acid Phosphoric acid Sodium chloride Sodium hydroxide, to 20% Sodium hydroxide, 40% Sulfuric acid, 50% Sulfuric acid, 80% Trichloroethylene Trisodium phosphate Xylene

R R R N N R R R R R R R R R R R N R R R R R C R R R

R R R N N R R R R R R R N R R R N R R C N R C R C R

RT, room temperature; R, recommended; N, not recommended; C, conditional.

This limitation is easily circumvented by using various membranes, primers, or mortar bedding systems that are compatible with the substrate. The process industries use lining systems (membranes) on most substrates onto which brick and tile are installed to ensure total resistance from aggressive environments encountered in such applications as 1. Pickling, plating, and galvanizing tanks in the steel and metalworking industries 2. Absorber towers in sulfuric acid plants 3. Scrubber in flu gas desulfurization applications 4. Floors in wet acid battery and chemical plants 5. Above-grade applications in dairies, food and beverage, and other processing plants



9

The versatility of furans is further exemplified by these available variations: 1. High-bond-strength materials for optimum physical mandates 2. Normal-bond-strength materials for economy and less demanding physical impositions 3. Hundred percent carbon filled for resistance to all concentrations of alkalies and most fluorine chemicals 4. Different ratios of carbon and silica for applications requiring varying degrees of electrical resistance or conductivity 1.3.1.3 Phenolics The origin of phenolic resins was in Europe dating back to the late 1800s. At the turn of the century, the only chemical-resistant mortar available was based on the inorganic silicates. These materials possess outstanding acid resistance but little or no resistance to many other chemicals. The silicates also exhibited significant physical limitations. After World War I, the limitation of the silicates prompted further investigation of the phenolics. These resins ceased to be laboratory curiosities and ultimately made their way into a multitude of applications because of their excellent physical properties. Early application for phenolic resins was for molding of telephones and associated electrical applications. By the 1930s, the chemical process and the steel and metalworking industries mandated more functional chemical-resistant mortars for installing chemical-resistant brick. Besides chemical resistance, they had to have excellent physical properties. By the mid-1930s, the first chemical-resistant phenolic resin mortar was introduced in the United States. It met the two most important mandates of the chemical, steel, and metalworking industries, i.e., 1. Provide resistance to high concentrations of acids and in particular to sulfuric acid at elevated temperatures 2. Provide low absorption with good bond strength to various types of brick, tile, and ceramics while possessing excellent tensile, flexural, and compressive properties To this day, phenolic resin mortars fulfill many of the requirements in the manufacture and use of the many grades and concentrations of sulfuric acid. The steel and metalworking industries continue to use phenolic resinbased, chemical-resistant mortars for brick-lined pickling, plating, and galvanizing applications. Phenolic resins are sufficiently functional to permit use of 100% carbon, 100% silica, or part silica and part carbon as fillers in phenolic mortars. Silica fillers are the most dominant for use in high concentrations of sulfuric acid


10

Corrosion of Linings and Coatings TABLE 1.5 Comparative Chemical Resistance: Phenolic Mortars vs. Furan Mortars Furan Medium, RT Amyl alcohol Chromic acid, 10% Gasoline Hydrofluoric acid, to 50% Hydrofluoric acid, 93% Methyl ethyl ketone Nitric acid, 10% Sodium hydroxide, to 5% Sodium hydroxide, 30% Sodium hypochlorite, 5% Sulfuric acid, to 50% Sulfuric acid, 93% Xylene

Phenolic

Carbon

Silica

Carbon

Silica

R N R R N R N R R N R N R

R N R N N R N R N N R N R

R N R R R R N N N N R R R

R N R N N R N N N N R R R

RT, room temperature; R, recommended; N, not recommended.

and where electrical resistance is required. Carbon fillers are used where resistance to high concentrations of hydrofluoric acid are required. They are also used as adhesive and potting compounds for corrosive electrical conductance applications. Phenolic mortars are similar to the furans in that they are two-component, easy-to-use mortars, with the acid catalyst or curing agent incorporated in the powder. Phenolic resins are seldom used to formulate grouts or monolithic surfacings. Phenolic resins have a limited shelf life and must be stored at 458F (78C). Phenolic resin mortars, like epoxies, can be allergenic to sensitive skin. This can be minimized or prevented by exercising good personal hygiene and using protective creams. Table 1.5 provides comparative chemical resistance for phenolic mortars compared to furan mortars, carbon vs. silica-filled. 1.3.1.4 Polyesters Chemical-resistant polyester mortar was developed and introduced in the early 1950s at the specific request of the pulp and paper industry. The request was for a mortar with resistance to a new bleach process utilizing chlorine dioxide. Polyester mortars ultimately became the premier mortar for use where resistance to oxidizing mediums is required. Unsaturated polyester resins are also used for formulating tile and machinery grouts as well as monolithic surfacing. These applications are formidable challenges for the formulator because of their propensity to cause shrinkage. Polyester mortars can be formulated to incorporate carbon and silica fillers depending on the end use intended. For applications requiring resistance to



11

hydrofluoric acid, fluorine chemicals, and strong alkalies, such as sodium and potassium hydroxide, 100% carbon fillers are required. Polyester resins are available in a number of types, the most popular of which are the following: 1. Isophthalic 2. Chlorendic acid 3. Bisphenol A fumarate The earliest mortars and grouts were based on the isophthalic polyester resin. This resin performed well in many oxidizing mediums. It did, however, present certain physical, thermal, and chemical resistance limitations. Formulations utilizing the chlorendic and bisphenol A fumarate resins offered improved chemical resistance, higher thermal capabilities, and improved ductility with less shrinkage. The bisphenol A fumarate resins offered significantly improved resistance to alkalies. They provided essentially equivalent resistance to oxidizing mediums. All polyester resin systems have provided outstanding chemical resistance to a multitude of applications in the pulp and paper, textile, steel and metalworking, pharmaceutical, and chemical process industries. Typical applications have been brick and tile floors, brick and tile lining in bleach towers, scrubbers, pickling and plating, and waste-holding and treating tanks. All the resins provide formulation flexibility to accommodate carbon and silica as fillers. Carbon- and silica-filled mortars and grouts are easily mixed and handled for the various types of installations. They are easily pigmented for aesthetic considerations. The essentially neutral curing systems provide compatibility for application to a multitude of substrates, i.e., concrete, steel, FRPs, etc. Properly formulated polyester resin systems provide installation flexibility to a wide range of temperatures, humidities, and contaminants encountered on most construction sites. They are one of the most forgiving of all of the resin systems. Polyester mortars and grouts have certain limitations that are inherent in all polyester formulations. They are as follows: 1. Strong aromatic odor that can be offensive for certain indoor and confined space applications 2. Shelf life limitations that can be controlled by low-temperature storage (below 608F [158C]) of the resin component Table 1.6 provides comparative chemical resistance for the previously enumerated polyester resins. The physical properties of the respective systems are of a magnitude that for most mortar and grout, tile, and masonry applications, they can be considered essentially equal.


12

Corrosion of Linings and Coatings TABLE 1.6 Comparison of Corrosion Resistance of Polyester Mortars Corrodent at Room Temperature

Polyestera Chlorendic

Bisphenol A Fumarate

U U R R R R R U R R R U R U U U

U U R R R U R U R U R R U U R U

Acetic acid, glacial Benzene Chlorine dioxide Ethyl alcohol Hydrochloric acid, 36% Hydrogen peroxide Methanol Methyl ethyl ketone Motor oil and gasoline Nitric acid, 40% Phenol, 5% Sodium hydroxide, 50% Sulfuric acid, 75% Toluene Triethanolamine Vinyl toluene a

R, recommended; U, unsatisfactory.

1.3.1.5 Vinyl Ester and Vinyl Ester Novolac Chemically, these resins are addition reactions of methacrylic acid and epoxy resin. The chemistry of these resins has prompted their being referred to as acrylated epoxies. They possess many of the properties of epoxy, acrylic, and bisphenol A fumarate polyester resins. Their similarity to these resins means that they exhibit the same outstanding chemical resistance and physical properties of mortars and grouts formulated from these resins. The vinyl esters are generally less rigid with lower shrinkage than many polyester systems. They favorably compare with the optimum chemicalresistant bisphenol A fumurate polyester mortars and grouts. The major advantage of the various vinyl ester systems are 1. Resistance to most oxidizing mediums 2. Resistance to high concentrations of sulfuric acid, sodium hydroxide, and many solvents The vinyl ester resin mortars have supplanted the polyester and have become the mortar of choice for brick-lined bleach towers in the pulp and paper industry. Like polyesters, vinyl ester formulations have similar inherent disadvantages: 1. Strong aromatic odor for indoor or confined space applications. Isolation of area where installations are being made may be



13

necessary to prevent in-plant ventilating systems from carrying the aromatic odor through the facility. 2. Shelf life limitations of the resin require refrigerated storage below 608F (158C) to extend useful life. Table 1.7 provides comparative chemical resistance for two types of polyester and vinyl ester resin mortar and grouts. 1.3.2 Inorganic Inorganic materials predate their organic counterparts, offer fewer choices, and consequently are somewhat easier to understand. The most popular materials are 1. Hot-pour sulfur mortars 2. Ambiently mixed and applied silicate mortars For years, all categories were referred to as “acid-proof mortars” because their capabilities are limited to a maximum pH of 7. They are not intended for alkaline or alternately acid and alkaline service.

TABLE 1.7 Comparative Chemical and Thermal Resistance of Polyester vs. Vinyl Ester Mortars and Grouts Polyester Medium, RT Acetic acid, glacial Benzene Chlorine dioxide Ethyl alcohol Hydrochloric acid, 36% Hydrogen peroxide Methanol Methyl ethyl ketone Motor oil and Gasoline Nitric acid, 40% Phenol, 5% Sodium hydroxide, 50% Sulfuric acid, 75% Toluene Triethanolamine Vinyl toluene Maximum temperature, 8F (8C)

Vinyl Ester

Chlorendic


Vinyl Ester

Novolac

C C R R R R R N R R R N R C N C 260 (127)

N N R R R N R N R N R R C N R N 250 (121)

N R R R R R N N R N R R R N R C 220 (104)

R R R R R R R N R R R R R R R R 230 (110)



14


1.3.2.1 Sulfur The initial application for sulfur mortars was to replace lead for joining bell and spigot cast iron water lines. Since then, sulfur mortars have been successfully used for installing brick floors, brick-lined tanks, and joining bell and spigot vitrified clay pipe for corrosive waste sewer lines in the chemical, steel, and metalworking industries. Sulfur mortars are plasticized to impart thermal shock resistance. They utilize 100% carbon or 100% silica fillers. Because of their outstanding resistance to oxidizing acids, the 100% carbon-filled sulfur mortar is the mortar of choice for installing carbon brick in the nitric/hydrofluoric acid picklers in the specialty steel industry. Both the 100% carbon and the 100% silica mortars have found widespread use in the plating, galvanizing specialty, and carbon steel industries. Advantages to using sulfur mortars when compared to some resin mortars are as follows: 1. Resistance to oxidizing, nonoxidizing, and mixed acids 2. Ease of use 3. High early strength; “cool it–use it” 4. Resistance to thermal shock 5. Unlimited shelf life 6. Prefabrication and in-place construction 7. Economy The many advantages of sulfur mortars make them ideal for applications such as setting of anchor bolts and posts, capping of concrete test cylinders, “proving” of molds for castings and hubs for grinding wheels. A disadvantage of sulfur mortars is flammability. When sulfur mortar masonry sheathings are being installed, melting equipment is placed outdoors and molten materials moved to the point of use, therefore minimizing potential for flammability problems. Installation of brick linings on vertical surfaces with sulfur mortars utilizes the concept of dry-laying brick by placing the brick on sulfur mortar spacer chips, papering the face of the brick to dam the joint, and pouring behind the brick to fill the joints. Horizontal surfaces are poured until the mortar comes up into the joints approximately 1/4 in. from the top of the brick. A final “flood pour” is made over the entire surface, therefore ensuring full flush joints. As soon as the joints cool, the installation is ready for service. Approximately 95% of the compressive value of sulfur mortars is attained 5 min after the mortar has solidified. Table 1.8 provides comparative chemical resistance to environments most commonly experienced in industries where sulfur mortars are used.



15

TABLE 1.8 Comparative Chemical Resistance: 100% Carbon vs. 100% SilicaFilled Sulfur Mortars Medium, RT Acetic acid, to 10% Aqua regia Cadmium salts Chromic acid, to 20% Gold cyanide Hydrochloric acid Hydrofluoric acid Iron salts Magnesium salts Methyl ethyl ketone Mineral spirits Nickel salts Nitric acid, to 40% Nitric/hydrofluoric acid Phosphoric acid Silver nitrate Sodium hydroxide Sodium salts Sulfuric acid, 80% Toluene Trichloroethylene Zinc, salts

100% Carbon

100% Silica

R N R R R R R R R N N R R R R R N R R N N R

R N R R R R N R R N N R R R R R N R R N N R

RT, room temperature; R, recommended; N, not recommended.

1.3.2.2 Silicates These mortars are most notable for their resistance to concentrated acids, except hydrofluoric acid and similar fluorinated chemicals, at elevated temperatures. They are also resistant to many aliphatic and aromatic solvents. They are not intended for use in alkaline or alternately acid and alkaline environments. This category of mortars includes 1. Sodium silicate 2. Potassium silicate 3. Silica (silica sol) The major applications for these mortars have been in the construction of sulfuric acid plants and the brick lining of stacks subjected to varying concentrations of sulfur and nitrogen oxides at elevated temperatures. Their upper thermal capabilities approach those of refractory mortars. The sodium and potassium silicate mortars are available as twocomponent systems, filler, and binder, with the setting agent in the filler.


16


Sodium and potassium silicates are referred to as soluble silicates because of their solubility in water. They are not affected by strong acids; however, this phenomenon precludes the use of many formulations in dilute acid service. However, this disadvantage becomes an advantage for formulating singlecomponent powder systems. All that is required is the addition of water at the time of use. Obviously, as the name of these materials implies, the fillers are pure silica. The sodium silicates can be produced over a broad range of compositions of the liquid binder. These properties and new hardening systems have significantly improved the water resistance of some sodium silicate mortars. These formulations are capable of resisting dilute as well as concentrated acids without compromising physical properties. The potassium silicate mortars are less versatile in terms of formulation flexibility. They are, however, less susceptible to crystallization in high concentrations of sulfuric acid so long as metal ion contamination is minimal. Potassium silicate mortars are available with halogen-free hardening systems, thereby eliminating the remote potential for catalyst poisoning in certain chemical processes. The silica or silica sol type of mortars are the newest of this class of mortars. They consist of a colloidal silica binder with quartz fillers. The principal difference compared to the other mortars is total freedom from metal ion that could contribute to sulfation hydration within the mortar joints in high-concentration sulfuric acid service. The workability and storage stability is comparable in the sodium and potassium silicates. The silica materials are harder to use, less forgiving as to mix ratio, and highly susceptible to irreversible damage because of freezing in storage. The chemical resistances of the various silicate mortars are very similar. Silicate mortars will fail when exposed to mild alkaline mediums such as bicarbonate of soda. Dilute acid solution, such as nitric acid, will have a deleterious effect on sodium silicates unless the water-resistant type is used. Table 1.9 shows the compatibility of various mortars with selected corrodents.

1.4 Chemical-Resistant Monolithic Surfacings and Polymer Concretes The chemistry of monolithic surfacings is an exploitation of the resin systems used for mortars and grouts. Additional systems will be included. To reiterate, monolithic surfacings are installed at thicknesses of 1/16 in. (1.5 mm) to 1/2 in. (13 mm). Polymer concretes are installed at thicknesses greater than 1/2 in. (13 mm). These materials are formidable corrosion



17

TABLE 1.9 Compatibility of Various Mortars with Selected Corrodents

(continued)


18 TABLE 1.9

Corrosion of Linings and Coatings Continued

(continued)



19

TABLE 1.9 Continued

(continued)


20 TABLE 1.9


(continued)



21

TABLE 1.9 Continued

(continued)


22 TABLE 1.9


(continued)



23

TABLE 1.9 Continued

(continued)


24 TABLE 1.9


(continued)



25

TABLE 1.9 Continued

(continued)


26 TABLE 1.9


(continued)



27

TABLE 1.9 Continued

(continued)


28 TABLE 1.9


(continued)



29

TABLE 1.9 Continued

(continued)


30 TABLE 1.9


(continued)



31

TABLE 1.9 Continued

(continued)


32 TABLE 1.9


(continued)



33

TABLE 1.9 Continued

(continued)


34


TABLE 1.9

Continued

The table is arranged alphabetically according to corrodent. Unless otherwise noted, the corrodent is considered pure, in the case of liquids, and a saturated aqueous solution in the case of solids. All percentages shown are weight percents. Corrosion is a function of temperature. When using the tables note that the vertical lines refer to temperatures midway between the temperatures cited. An entry of R indicates that the material is resistant to the maximum temperature shown. An entry of U indicates that the material is unsatisfactory. A blank indicates that no data are available.

barriers. Monolithic surfacings are not intended to replace brick floors in heavy-duty chemical or physical applications. However, they are economical corrosion barriers for a broad range of applications. The most popular monolithic surfacings are formulated from the following resins: 1. Epoxy including epoxy Novolac 2. Polyester 3. Vinyl ester, including vinyl ester Novolac 4. Acrylic 5. Urethane, rigid and flexible Chemical-resistant polymer concretes are formulated from some of the same generic resins. The more popular resins used are 1. Furan 2. Epoxy, including epoxy Novolac 3. Polyester 4. Vinyl ester, including vinyl ester Novolac 5. Acrylics 6. Sulfur



35

The major advantages to be derived from the use of chemical-resistant monolithic surfacings and polymer concretes are as follows: 1. These formulations provide flexibility, giving aesthetically attractive materials with a wide range of chemical resistances, physical properties, and methods of application. 2. These formulations provide high early development of physical properties. Compressive values with some systems reach 5,000 psi (35 MPa) in 2 h and 19,000 psi (133 MPa) as ultimate compressive value. 3. Most systems are equally appropriate for applications to new and existing concrete including pour-in-place and precasting. 4. Systems offer ease of installation by in-house maintenance personnel. 5. Systems offer economy when compared to many types of brick and tile installations. 6. Systems are available for horizontal, vertical, and overhead applications. Furan polymer concrete is inherently brittle and, in large masses, has a propensity to shrink. It is used when resistance to acids, alkalies, and solvents such as aromatic and aliphatic solvents is required. It has been successfully used in small areas in the chemical, electronic, pharmaceutical, steel, and metal working industries. Polyester, vinyl ester, and acrylic polymer concrete have strong aromatic odors that can be offensive to installation and in-plant personnel. Fire codes, particularly for acrylics, must be scrutinized to ensure compliance. Sulfur cement polymer concrete is flammable; consequently, the potential for oxides of sulfur would preclude its use for most indoor applications. Sulfur cement polymer concrete is not recommended as a concrete topping. Polymer concretes are not to be misconstrued with polymer-modified Portland cement concrete. Polymer concretes are totally chemical-resistant, synthetic resin compounds with outstanding physical properties. Polymer concretes pass the total immersion test at varying temperatures for sustained periods. Polymer-modified Portland cement concrete can use some of the same generic resins as used in polymer concretes, but with different results. The major benefits to be derived from polymer-modified Portland cement concrete are as follows: 1. They permit application of concrete in thinner cross-sections. 2. They provide improved adhesion for pours onto existing concrete. 3. They lower absorption of concrete. 4. They improve impact resistance.


36


5. They improve resistance to salt but not to aggressive corrosive chemicals such as hydrochloric or sulfuric acid. The success of monolithic surfacing installations is very much predicated on the qualifications of the design, engineering, and installation personnel, be they in-house or outside contractors. The following fundamental rules are important to the success of any monolithic surfacing installation: 1. Substrate must be properly engineered to be structurally sound, free of cracks, and properly sloped to drains. 2. New as well as existing slabs must be clean and dry, free of laitance and contaminants, with a coarse surface profile. 3. Ambient slab and materials to be installed should be 65–858F (18–298C). Special catalyst and hardening systems are available to accommodate higher or lower temperatures, if required. 4. Thoroughly prime substrate before applying any monolithic surfacing. Follow manufacturer’s instructions. 5. Thoroughly mix individual and combined components at a maximum speed of 500 rpm to minimize air entrainment during installation. 6. Uncured materials must be protected from moisture and contamination. Monolithic surfacings are unique, versatile materials used primarily as flooring systems. They are available in a variety of formulations to accommodate various methods of application. They employ many of the installation methods that have been successfully utilized in the Portland cement concrete industry. The most popular methods are: 1. Hand-troweled 2. Power-troweled 3. Spray 4. Pour-in-place/self-level 5. Broadcast Hand-troweled applications are approximately 1/4 in. (6 mm) thick and are suggested for small areas or areas with multiple obstructions such as piers, curbs, column foundations, trenches, and sumps. The finished application is tight and dense, and it has a high-friction finish. Topcoat sealers are recommended to provide increased density and imperviousness with a smooth, easy-to-clean finish. High- and low-friction finishes are easily accomplished predicated on end use requirements.



37

Power trowel installations are the fastest, most economical method for large areas with minimum obstructions. Minimum thickness is 1/4 in. (6 mm). Appropriate sealers are available to improve density of finish. Spray applications are also ideal for areas where corrosion is aggressive. Spray applications are applied, minimum 1/8 in. (3 mm) thick, in one pass on horizontal surfaces. On vertical and overhead areas including structural components, the material can be spray-applied 1/16 to 3/32 in. thick (1.5–2.4 mm) in one pass and without slump. The mortarlike consistency of the material can be varied to control slump and type of finish. Floors installed in this manner are dense, smooth, safe finishes for people and vehicular traffic. Pour-in-place and self-level materials are intended for flat areas where the pitch to floor drains and trenches are minimal. They are intended for light-duty areas with minimum process spills. The completed installation is 1/8 to 3/16 in. (3–5 mm) thick with a very smooth, high-gloss, easy-to-clean, aesthetically attractive finish. Broadcast systems are simple to install, economical, aesthetically attractive floors applied in thicknesses of 3/32 to 1/8 in. (2–3 mm). Resins are squeegee-applied to the concrete slab into which filler and colored quartz aggregates of varying color and size are broadcast or sprinkled into the resin. After the resin has set, the excess filler and quartz aggregate is removed by vacuuming or sweeping for reuse. The process is repeated until the desired floor thickness is achieved. The finished floor is easy to clean and outstanding for light industrial, laboratory, cleanroom, and institutional applications.

1.4.1 Chemical Resistance Monolithic surfacings and polymer concretes mirror image the chemical resistance of their mortar and grout counterparts. Refer to corrosion tables previously presented and Table 1.10 which follows. Table 1.10 provides comparative chemical resistance for the most popular resins used as monolithic surfacings and polymer concrete. Those systems without chemical-resistant mortar and grout counterparts are as follows: 1. Acrylic 2. Urethane, rigid and flexible Acrylic monolithic surfacing and polymer concretes are installed in thicknesses of 1/8 to 1/2 in. (3–13 mm) and 1/2 in. (13 mm) and greater, respectively. These flooring systems are an extension of methyl methacrylate chemistry popularized by Rohm and Haas Co.’s Plexiglass and Dupont’s Lucite. They are intended for protection against moderate corrosion environments.


38


TABLE 1.10 Comparative Chemical Resistance 1-AZbisphenol A epoxy—aliphatic amine hardener 1-BZbisphenol A epoxy—aromatic amine hardener 1-CZbisphenol F epoxy (epoxy novolac) 2-DZpolyester resin—chlorendic acid type 2-EZpolyester resin—bisphenol A fumarate type 3-FZvinyl ester resin 3-GZvinyl ester novolac resin 1

2

3

Medium, RT

A

B

C

D

E

F

G

Acetic acid, to 10% Acetic acid, 10–15% Benzene Butyl alcohol Chlorine, wet, dry Ethyl alcohol Fatty acids Formaldehyde, to 37% Hydrochloric acid, to 36% Kerosene Methyl ethyl ketone, 100% Nitric acid, to 20% Nitric acid, 20–40% Phosphoric acid Sodium hydroxide, to 25% Sodium hydroxide, 25–50% Sodium hypochlorite, to 6% Sulfuric acid, to 50% Sulfuric acid, 50–75% Xylene

R C C R C R C R C R N N N R R R C R C N

R R R C C C R R R R N N N R R C R R R R

R C R R C R C R R R N R R R R R R R R R

R R R R R R R R R R N R R R N N R R R R

R R N R R R R R R R N R N R R R R R C R

R C R N R R R R R R N R N R R C R R R N

R R R R R R R R R R N R C R R R R R R R


The principal advantages for their use are as follows: 1. They are the easiest of the resin systems to mix and apply by using pour-in-place and self-leveling techniques. 2. Because of their outstanding weather resistance, they are equally appropriate for indoor and outdoor applications. 3. They are the only system that can be installed at below freezing temperatures, 258F (K48C), without having to use special hardening or catalyst systems. 4. They are the fastest set and cure of all resin systems. The monolithics will support foot and light-wheeled traffic in 1 h, whereas, the thicker cross-section polymer concrete will also



39

support foot and light-wheeled traffic in 1 h while developing 90% of its ultimate strength in 4 h. 5. They are the easiest to pigment and with the addition of various types of aggregate, they can be aesthetically attractive. 6. They are equally appropriate for maintenance and newconstruction applications. They bond well to concrete. They are ideal for rehabilitating, manufacturing, warehouse, and loading dock floors to impart wear resistance and ease of cleaning. As previously indicated, a disadvantage inherent in acrylic systems is the aromatic odor for indoor or confined space applications. The urethane systems are intended to be monolithic floors with elastomeric properties installed in thicknesses of 1/8 to 1/4 in. (3–6 mm). Similar to the acrylic systems, the urethanes are intended for protection against moderate to light corrosion environments. Standard systems are effective at temperatures of 10–1408F (K24 to 608C). High-temperature systems are available for exposure to temperatures of 10–1808F (K24 to 828C). Many of the urethane systems are capable of bridging cracks up to 1/16 in. (1.6 mm). The monolithic urethane flooring systems offer the following advantages: 1. They are easy to mix and apply using the pour-in-place, self-level application technique. 2. Systems are available for indoor and outdoor applications. 3. The elastomeric quality of the systems provides underfoot comfort for production line flooring applications. 4. Because of their being elastomeric, they have excellent sounddeadening properties. 5. They have outstanding resistance to impact and abrasion. 6. They are excellent waterproof flooring systems for above-grade light- and heavy-duty floors. They are equally appropriate for maintenance and new-construction applications. 7. They are capable of bridging cracks in concrete 1/16 in. (1.5 mm) wide. Urethane materials are demanding systems during installation. Mix ratio of components, temperature, and humidity controls are mandatory for successful installations. The comparative chemical resistances of acrylic and urethane systems are presented in Table 1.11. The physical properties of acrylic systems are substantially different from those of the urethanes. The acrylic flooring systems are extremely hard and should be considered too brittle for applications subjected to excessive physical abuse such as impact from large-diameter steel pipe, steel plate,


40


TABLE 1.11 Comparative Chemical Resistance: Urethane vs. Acrylic Systems Urethane Medium, RT Acetic acid, 10% Animal oils Boric acid Butter Chromic acid, 5–10% Ethyl alcohol Fatty acids Gasoline Hydrochloric acid, 20–36% Lactic acid, above 10% Methyl ethyl ketone, 100% Nitric acid, 5–10% Sulfuric acid, 20–50% Water, fresh Wine

Acrylic

Standard

High-Temperature

G G E G C N F E F F N G G E G

G G E F C N F N C C N C C E G

C N E N C N N N C C N F C E F

RT, room temperature; E, excellent; G, good; F, fair; C, conditional, N; not recommended.

and heavy castings. The inherent flexibility and impact resistance of urethanes offer potential for these types of applications. Precast and poured-in-place polymer concrete has been successfully used in a multitude of indoor and outdoor applications in various industries. Acrylic polymer concrete has been used for precast trenches and covers, delta bus supports, and insulators. Ease of pigmenting to match corporate colors, good weather resistance, resistance to airborne SO2, SO3, and NOX, and dielectric properties have made acrylics particularly attractive in the electric utility industry. The chemical, steel, electronic, automotive, and pharmaceutical industries have taken advantage of the ease of mixing and placing, as well as the high early strength and chemical resistance properties, of various polymer concretes. 1.4.2 Applications Carbon steel and reinforced concrete are outstanding general construction materials. They have an enviable record of success in a multitude of industries and applications. Unfortunately, steel and concrete will corrode when oxygen and water are present. Weather and chemicals are catalysts that accelerate the corrosion process. The cost attributable to corrosion in the United States is estimated to be in a range of $9–$90 billion. This figure was confirmed from a study initiated



41

several years ago by the National Institute of Standards and Technology (formerly National Bureau of Standards). The range includes corrosion attributable to chemical processes, to corrosion of highways and bridges from de-icing chemicals, to atmospheric corrosion of a steel fence. The economic losses attributable to corrosion are confirmed by various technical organizations such as NACE International and others. Chemical-resistant mortars, grouts, and monolithic surfacings are used for protecting steel and concrete in a host of applications. Chemical-resistant mortars and grouts for installing all sizes and shapes of brick, tile, and ceramics provide the premier thermal, physical, and chemical-resistant sheathing for protecting linings and membranes applied to steel and concrete. Typical applications include the following: 1. Below, on, and above grade floors 2. Pickling, plating, storage, and chemical process tanks and towers 3. Waste holding and treatment tanks 4. Dual containment for outdoor process and storage vessels, including leak detection systems 5. Stacks and scrubbers from incineration and treatment of toxic waste fumes 6. Above- and below-grade trenches, pipelines, sumps, and manholes Polymer concretes can be used as fast-set, totally chemical-resistant, poured-in-place slabs or as a topping for refurbishing of existing concrete slabs. They are highly chemical-resistant materials of exceptional physical properties that can also be used for a multitude of precast applications such as curbs, piers, foundations, pump pads, stair treads, trenches and covers, sumps, and manholes. Chemical-resistant, nonmetallic construction materials are formidable, economical corrosion barriers for protecting steel and concrete when compared to most alloys. Nonmetallic construction systems can incorporate in their design dual containment and leak detection to meet all federal and state environmental mandates. The pursuit of clean air and water will continue unabated. Environmental laws will continue to be stringent. Recycling, waste treatments, and incineration will require close attention to corrosivity of all processes. The agricultural industry, producers of various fertilizers and agricultural chemicals, relies on brick-lined floors and tanks in the production of sulfuric and phosphoric acids. Chemical storage and waste treatment facilities require protection from aggressive chemicals and waste byproducts. The pharmaceutical, food, and beverage industries are plagued by corrosion from chemicals and food acids as well as corrosion from acid


42


and alkaline cleaning and sanitizing chemicals. The Food and Drug Administration and U.S. Department of Agriculture will be unrelenting in upholding sanitation mandates to ensure the health and welfare of the population. The healthcare industry is under severe cost containment pressure. The best cost containment in the food, beverage, and pharmaceutical industries is their continued high standards of excellence in maintaining standards of cleanliness. Maintaining these standards is not without cost from corrosion to concrete and steel. Chemical-resistant mortars, grouts, monolithic surfacings, and polymer concrete are proven solutions to a host of these types of corrosion problems.


2 Cathodic Protection

2.1 Introduction A tremendous investment exists world-wide in underground metallic structures such as pipelines, storage facilities, well casings, structure supports, communication cables, etc. When these members are in direct contact with the soil and unprotected, they are subject to corrosion. Attempts have been made to overcome this problem by the use of various types of coatings applied to the surface. Although such coatings can be effective, invariably small holes or holidays are usually present. These holidays provide access to the uncovered base metal and permit corrosion. Subsequent repairs can be extremely costly. In addition, undetected failure (or leakage) can cause accidents or lead to safety hazards, such as causing roadways to collapse as a result of an underground water leak, or to environmental hazards resulting from oil leaks. By cathodic protection, bare metals and holidays in coated metals can be protected from corrosion.

2.2 Background Cathodic protection is a major factor in metals’ corrosion control. When an external electric current is applied, the corrosion rate can be reduced to practically zero. Under these conditions, the metal can indefinitely remain in a corrosive environment without deterioration. In practice, cathodic protection can be utilized with such metals as steel, copper, brass, lead, and aluminum against corrosion in all soils and almost all aqueous media. Although it cannot be used above the waterline (because the impressed electric current cannot reach areas outside of the electrolyte), 43


44


it can effectively be used to eliminate corrosion fatigue, intergranular corrosion, stress-corrosion cracking, dezincification of brass, or pitting of stainless steels in seawater or steel in soil. In 1824, Sir Humphry David reported that by coupling iron or zinc to copper, the copper could be protected against corrosion. The British Admiralty had blocks of iron attached to the hulls of copper-sheathed vessels to provide cathodic protection. Unfortunately, cathodically protected copper is subject to fouling by marine life, which reduced the speed of vessels under sail and forced the admiralty to discontinue the practice. However, the corrosion rate of the copper had been appreciably reduced. Unprotected copper supplies a different number of copper ions to poison fouling organisms. In 1829, Edmund Davy was successful in protecting the iron portions of buoys by using zinc blocks, and in 1840, Robert Mallete produced a zinc alloy that was particularly suited as a sacrificial anode. The fitting of zinc slabs to the hulls of vessels became standard practice as wooden hulls were replaced. This provided localized protection, specifically against the galvanic action of a bronze propeller. Overall protection of seagoing vessels was not investigated until 1950 when the Canadian Navy determined that the proper use of anti-fouling paints in conjunction with corrosion resistant paints made cathodic protection of ships feasable and could reduce maintenance costs. About 1910–1912 the first application of cathodic protection by means of an impressed current was undertaken in England and the United States. Since that time, the general use of cathodic protection has been widespread. There are thousands of miles of buried pipe and cables that are protected in this manner. This form of protection is also used for water tanks, submarines, canal gates, marine piling, condensers, and chemical equipment.

2.3 Theory Cathodic protection is achieved by applying electrochemical principles to metallic components buried in soil or immersed in water. It is accomplished by flowing a cathodic current through a metal–electrolyte interface favoring the reduction reaction over the anodic metal dissolution. This enables the entire structure to work as a cathode. The flux of electrons can be provided by one of two methods. By use of a rectifier, a direct current may be impressed on an inert anode and the components. These components receive an excess of electrons and are, thereby, cathodically protected. The alternative method is to couple the components with a more active metal, such as zinc or magnesium, to create a galvanic cell. Under these conditions, the active metal operates as an anode and is destroyed while protecting the components that are cathodic. Such an anode is referred to as a sacrificial anode.


Cathodic Protection

45

Potential

f Cu

I(max)Re

f (corros.)

f Zn

I(max)

Current FIGURE 2.1 Polarization for copper–zinc cell.

The basis of cathodic protection is shown in the polarization diagram for a Cu–Zn cell (Figure 2.1). If polarization of the cathode is continued by use of an external current beyond the corrosion potential to the open-circuit potential of the anode, both electrodes reach the same potential and no corrosion of the zinc can take place. Cathodic protection is accomplished by supplying an external current to the corroding metal on the surface of which local action cells operate as shown in Figure 2.2. Current flows from the auxiliary anode and enters the anodic and cathodic areas of the corrosion B −

+

+ − +

Electrolyte

Corroding metal

Auxiliary anode

FIGURE 2.2 Cathodic protection using impressed current on local action cell.


46


cells, returning to the source of the DC current, B. Local action current will cease to flow when all the metal surface is at the same potential as a result of the cathode areas being polarized by an external current to the open-current potential of the anodes. As long as this external current is maintained, the metal cannot corrode. The corrosion rate will remain at zero if the metal is polarized slightly beyond the open circuit potential of the anode. However, this excess current has no value and may be injurious to amphoteric metals or coatings. Therefore, in actual practice, the impressed current is maintained close to the theoretical minimum. If the current should fall below that required for complete protection, some protection will still be afforded.

2.4 Method of Application A source of direct current and an auxiliary electrode are required to provide cathodic protection. The auxiliary electrode (anode) is usually composed of graphite or iron and is located some distance away from the structure being protected. The anode is connected to the positive terminal of the DC source, and the structure being protected is connected to the negative terminal. This permits current to flow from the anode, through the electrolyte, to the structure. Applied voltages are not critical as long as they are sufficient to supply an adequate current density to all parts of the protected structure. The resistivity of the soil will determine the required applied voltage; when the end of a long pipeline is to be protected, the voltage will have to be increased. Current is usually supplied by a rectifier supplying low-voltage direct current of several amperes. 2.4.1 Impressed Current Systems For impressed current systems, the source of electricity is external. A rectifier converts high voltage AC current to low voltage DC current. This direct current is impressed between buried anodes and the structure to be protected. It is preferred to use inert anodes that will last for the longest possible times. Typical materials used for these anodes are graphite, silicon, titanium, and niobium plated with platinum. For a given applied voltage, the current is limited by electrolyte resistivity and by the anodic and cathodic polarization. With the impressed current system, it is possible to impose whatever potential is necessary to obtain the current density required by means of the rectifier. Electric current flows in the soil from the buried anode to the underground structure to be protected. Therefore, the anode must be connected to the positive pole of the rectifier and the structure to the negative pole. All cables


Cathodic Protection

47

from the rectifier to the anode and to the structure must be electrically insulated. If not, those from the rectifier to the anode will act as an anode and deteriorate rapidly, whereas, those from the rectifier to the structure may pick up some of the electric current that would then be lost for protection. 2.4.1.1 Current Requirements The specific metal and environment will determine the current density required for complete protection. The applied current density must always exceed the current density equivalent to the measured corrosion rate under the same conditions. Therefore, as the corrosion rate increases, the impressed current density must be increased to provide protection. There are several factors that affect the current requirements. These include: 1. The nature of the electrolyte 2. The soil resistivity 3. The degree of aeration The more acidic the electrolyte, the greater the potential for corrosion and the greater the current requirement. Soils that exhibit a high resistance require a lower cathode current to provide protection. However, in areas of violent agitation or high aeration, an increase in current will be required. The required current to provide cathodic protection can vary from 0.5 to 20 mA/ft.2 of bare surface. Field testing may be required to determine the necessary current density to provide cathodic protection in a specific area. However, these testing techniques will provide only an approximation. After completion of the installation, it will be necessary to conduct a potential survey and make necessary adjustments to provide the desired degree of protection. For cathodically controlled corrosion rates, the corrosion potential approaches the open-circuit anodic potential, and the required current density is only slightly greater than the equivalent corrosion current. The required current can be considerably greater than the corrosion current for mixed control, and for anodically controlled corrosion reactions, the required current is even greater. When a protective current causes precipitation of an inorganic scale on the cathode surface, such as in hard water or seawater, the total current required is gradually reduced. This is the result of an insulating coating being formed. However, the current density at the exposed metal areas does not change; only the total current density per apparent unit area is less. 2.4.2 Sacrificial Anodes It is possible, by selection of an anode constructed of a metal more active in the galvanic series than the metal to be protected, to eliminate the need


48


for an external DC current. A galvanic cell will be established with the current direction, exactly as described, by using an impressed electric current. These sacrificial anodes are usually composed of magnesium or magnesium-based alloys. Occasionally, zinc and aluminum have been used. Because these anodes are essentially sources of portable electrical energy, they are particularly useful in areas where electric power is not available or where it is uneconomical or impractical to install power lines for this purpose. Most sacrificial anodes in use in the United States are of magnesium construction. Approximately 10 million pounds of magnesium is annually used for this purpose. The open-circuit potential difference between magnesium and steel is about 1 V. This means that one anode can protect only a limited length of pipeline. However, this low voltage can have an advantage over higher impressed voltages in that the danger of overprotection to some portions of the structure is less, and, because the total current per anode is limited, the danger of stray-current damage to adjoining metal structures is reduced. Magnesium anode rods have also been placed in steel hot-water tanks to increase the life of these tanks. The greatest degree of protection is afforded in “hard” waters where the conductivity of the water is greater than in “soft” waters. 2.4.2.1 Anode Requirements To provide cathodic protection, a current density of a few milliamps (mA) is required. Therefore, to determine the anodic requirements, it is necessary to know the energy content of the anode and its efficiency. From this data, the necessary calculations can be made to size the anode, determine its expected life, and determine the number of anodes required. As previously indicated, the three most common metals used as sacrificial anodes are magnesium, zinc, and aluminum. The energy content and efficiency of these metals are as follows:

Metal

Theoretical Energy Content (A h/lb)

Anodic Efficiency (%)

Practical Energy (PE) Constant (A h/lb)

Magnesium Zinc Aluminum

1000 370 1345

50 90 60

500 333 810

The number of pounds of metal required to provide a current of 1 A for a year can be obtained from the following equation: lb metal=A

yr Z

8760 h=yr : PE


Cathodic Protection

49

For magnesium this would be lb Mg=A

yr Z

8760 Z 17:52: 500

The number of years (YN) for which 1 lb of metal can produce a current of 1 mA is determined from the following equation: YN Z

PE : 10 A 8760 h=yr K3

For magnesium this would be 500 Z 60 years: 10K3 ð8760Þ The life expectancy (L) of an anode of W lb, delivering a current of i mA is calculated as follows: LZ

YNðWÞ : i

For magnesium this would be LMg Z

60ðWÞ i

that is based on a 50% anodic efficiency. Because actual efficiencies tend to be somewhat less, it is advisable to apply a safety factor and multiply the result by 0.75. The current required to secure protection of a structure and the available cell voltage between the metal structure and sacrificial anode determine the number of anodes required. This can be illustrated by the following example: Assume that an underground pipeline has an external area of 200 ft.2 and a soil resistivity of 600 Ocm. Field tests indicate that 6 mA/ft.2 is required for protection. To provide protection for the entire pipeline (6 mA/ft.2) (200 ft.2)Z1200 mA. Magnesium anodes used in this particular soil have a voltage of K1.65 V, or a galvanic cell voltage of Ecell Z EC KEA ZK0:85KðK1:65Þ Z C0:8 V: The resistance is therefore RZ

V 0:8 Z Z 0:67 U: I 1:2



Resistance

50

Number of anodes FIGURE 2.3 Plot of Sunde equation.

As the number of anodes are increased, the total resistance of the system decreases. Each anode that is added provides a new path for current flow, parallel to the existing system. The relationship between the resistance of the system and the number of anodes is shown in the Sunde equation. RZ

0:00521P 8L 2L 2:3 log C 2:3 log 0:656N ; NL dK1 S

where R, resistance in O; P, soil resistivity in Ocm; N, number of anodes; L, anode length (ft.); d, diameter of anode (ft.); S, distance between anodes (ft.). Figure 2.3 shows the typical plotting of the results of this equation. Different anodic shapes will have different curves. 2.4.2.2 Anode Materials and Backfill The use of magnesium as a sacrificial anode has already been discussed. For use with impressed current, auxiliary anodes are usually formed of scrap iron or graphite. Scrap iron is consumed at a considerably faster rate than graphite (15–20 lb/A-yr vs. 2 lb/A-yr); however, graphite costs more both initially and in operating expense. Graphite requires more power than scrap iron. It is also more fragile, and greater care must be taken during installation. Under certain conditions, the advantage of the 8- to 10-times longer life far outweighs the added costs, particularly in areas where replacement poses problems.


Cathodic Protection

51

Platinum-clad or 2% silver–lead electrodes that use impressed current have been employed for the protection of structures in seawater. The latter anodes are estimated to last ten years, whereas, sacrificial magnesium anodes require replacement every two years. On occasion, aluminum electrodes have been used in freshwaters. Because the effective resistivity of soil surrounding an anode is limited to the immediate area of the electrode, this local resistance is generally reduced by using backfill. For impressed current systems, the anode is surrounded with a thick bed of coke mixed with three to four parts of gypsum to one part of sodium chloride. The consumption of the anode is reduced somewhat because the coke backfill is a conductor and carries part of the current. If the anode is immersed in a river bed, lake, or ocean, backfill is not required. Auxiliary anodes need not be consumed to fulfill their purpose. Conversely, sacrificial anodes are consumed no less to supply an equivalent current than is required by Faraday’s law. For magnesium anodes, backfill has the advantage of reducing the resistance of insulating corrosion-product films as well as increasing the conductivity of the immediate area. A typical backfill consists of a mixture of approximately 20% bentonite (for retention of moisture), 75% gypsum, and 5% sodium sulfate.

2.5 Use with Coatings Insulating coatings are advantageous to use with either impressed current or sacrificial anodes when supplying cathodic protection. These coatings need not be pore free because the protective current flows preferentially to the exposed metal areas that require the protection. Such coatings are useful in distributing the protective current, in reducing total current requirements, and in extending the life of the anode. For example, in a coated pipeline, the current distribution is greatly improved over that of a bare pipeline, the number of anodes and total current required is less, and one anode can protect a much longer section of pipeline. Because the earth is a good electrical conductor and the resistivity of the soil is localized only within the region of the pipeline or electrodes, the limiting length of pipe protected per anode is imposed by the metallic resistance of the pipe and not the resistance of the soil. One magnesium anode is capable of protecting approximately 100 ft. (30 m) of a bare pipeline, whereas, it can provide protection for approximately 5 miles (8 km) of a coated pipeline. In a hot-water tank coated with glass or an organic coating, the life of the magnesium anode is extended and more uniform protection is supplied to the tank. Without the coating, the tendency is for excess current to flow to


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the side and insufficient current flows to the top and bottom. Because of these factors cathodic protection is usually provided with coated surfaces.

2.6 Testing for Completeness of Protection There are several ways that the effectiveness of protection can be checked. The first two methods are qualitative and do not provide data about whether enough or more than enough current is being supplied. Potential measurements, the third method, is of prime importance in practice. 2.6.1 Coupon Tests A metal coupon is shaped to conform to the contour of the pipe, weighed, and attached by a brazed-connected cable to the pipe. Both the cable and the surface between the coupon and pipe are coated with coal tar. The coupon is allowed to remain buried for weeks or months, recovered, cleaned, and weighed. The weight loss, if any, is an indication of whether or not the cathodic protection of the pipeline is complete. 2.6.2 Colormetric Tests A piece of absorbent paper soaked in potassium ferricyanide solution is placed in contact with a cleaned section of the buried pipeline and the soil replaced. After a relatively short time, the paper is retrieved. A blue ferrous ferricyanide reaction indicates incomplete cathodic protection, whereas, an absence of blue on the paper indicates that the cathodic protection is complete. 2.6.3 Potential Measurements By measuring the potential of the protected structure, the degree of protection, including overprotection, can be quantitatively determined. This measurement is the generally accepted criterion and is used by corrosion engineers. The basis for this determination is the fundamental concept that cathodic protection is complete when the protected structure is polarized to the open-circuit anodic potential of local action cells. The reference electrode for making this measurement should be placed as closely as possible to the protected structure to avoid and to minimize an error caused by internal resistance (IR) drop through the soil. Such IR drops through corrosion product films or insulating coatings will still be present regardless of precautions taken, tending to make the measured potential more active than the actual potential at the metal surface. For buried pipelines, a compromise location is taken directly over the buried pipe at the soil surface because cathodic protection currents flow mostly to


Cathodic Protection

53

TABLE 2.1 Calculated Minimum Potential, f, for Cathodic Protection Metal

E8 (V)

Solubility Product, M(OH)2

fH2 Scale (V)

f vs. Cu–CuSO4 Reference Electrode (V)

Iron Copper Zinc Lead

0.440 K0.337 0.763 0.126

1.8!10K15 1.6!10K19 4.5!10K17 4.2!10K15

K0.59 0.16 K0.93 K0.27

K0.91 K0.16 K1.25 K0.59

Source: From H.H. Uhlig. 1971. Corrosion and Corrosion Control, 2nd ed., New York: Wiley.

the lower surface and are minimum at the upper surface of the pipe buried a few feet below the soil surface. The potential for steel is equal to K0.85 V vs. the copper-saturated copper sulfate half-cell, or 0.53 V on the standard hydrogen scale. The theoretical open-circuit anodic potential for other metals may be calculated using the Nernst equation. Several typical calculated values are shown in Table 2.1.

2.7 Overprotection Overprotection of steel structures, to a moderate degree, usually does not cause any problems. The primary disadvantages are waste of electric power and increased consumption of auxiliary anodes. When the overprotection is excessive, hydrogen can be generated at the protected structure in sufficient quantities to cause blistering of organic coatings, hydrogen embrittlement of the steel, or hydrogen cracking. Damage to steel by hydrogen absorption is more prevalent in environments where sulfides are present. Overprotection of systems with amphoteric metals (e.g., aluminum, zinc, lead, and tin) will damage the metal by causing increased attack instead of reduction of corrosion. This emphasizes the need for making potential measurements of protected structures.

2.8 Economics The cost of cathodic protection is more than recovered by reduced maintenance costs or by reduced installation costs, or both. For buried pipelines, the guarantee that there will be no corrosion on the soil side of the pipe has made it economically feasible to transport oil and high-pressure natural gas across the American continent. It has also permitted the use of thinner-walled pipe. Wall thicknesses need only be sufficient to withstand


54


the internal pressures. No extra allowance has to be added for external corrosion. This saving alone has sometimes more than paid for the installation of the cathodic protection equipment. Similarly, other cathodic protection systems have more than paid for their installation costs by reduced maintenance costs or by longer operating periods between routine inspections and maintenance periods.


3 Corrosion Inhibitors

3.1 Introduction Corrosion of metallic surfaces can be reduced or controlled by the addition of chemical compounds to the corrodent. This form of corrosion control is called inhibition and the compounds added are known as corrosion inhibitors. These inhibitors will reduce the rate of either anodic oxidation or cathodic reduction, or both. The inhibitors themselves form a protective film on the surface of the metal. It has been postulated that the inhibitors are adsorbed into the metal surface either by physical (electrostatic) adsorption or chemosorption. Physical adsorption is the result of electrostatic attractive forces between the organic ions and the electrically charged metal surface. Chemosorption is the transfer, or sharing of the inhibitor molecule’s charge to the metal surface, forming a coordinate-type bond. The adsorbed inhibitor reduces the corrosion rate of the metal surface either by retarding the anodic dissolution reaction of the metal by the cathodic evolution of hydrogen, or both. Inhibitors can be used at pH values of acid from near neutral to alkaline. They can be classified in many different ways according to 1. Their chemical nature (organic or inorganic substances) 2. Their characteristics (oxidizing or nonoxidizing compounds) 3. Their technical field of application (pickling, descaling, acid cleaning, cooling water systems, and the like) The most common and widely known use of inhibitors is their application in automobile cooling systems and boiler feedwaters. By considering the electrochemical nature of corrosion processes, constituted by at least two electrochemical partial reactions, inhibition may be defined on an electrochemical basis. Inhibitors will reduce the rates 55

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of either or both of these partial reactions (anodic oxidation and/or cathodic reduction). As a consequence, there can be anodic, cathodic, and mixed inhibitors. Other tentative classification of inhibitors have been made by taking into consideration the chemical nature (organic or inorganic substances), their characteristics (oxidizing or nonoxidizing compounds), or their technological field of application (pickling, descaling, acid cleaning, cooling water systems, etc.). Inhibitors can be used in electrolytes at different pH values, from acid to near-neutral or alkaline solutions. Because of the very different situations created by changing various factors such as medium and inhibitor in the system metal/aggressive medium/inhibitor, various inhibition mechanisms must be considered.1–6 An accurate analysis of the different modes of inhibiting electrode reactions including corrosion was carried out by Fischer.7 He distinguished among various mechanisms of action such as: Interface inhibition Electrolyte layer inhibition Membrane inhibition Passivation Subsequently, Lorenz and Mansfield8 proposed a clear distinction between interface and interphase inhibition, representing two different types of retardation mechanisms of electrode reactions including corrosion. Interface inhibition presumes a strong interaction between the inhibitor and the corroding surface of the metal.1,7,9 In this case, the inhibitor adsorbs as a potential-dependent, two-dimensional layer. This layer can affect the basic corrosion reactions in different ways: By a geometric blocking effect of the electrode surface because of the adsorption of a stable inhibitor at a relatively high degree of coverage of the metal surface By a blocking effect of the surface sites because of the adsorption of a stable inhibitor at a relatively low degree of coverage By a reactive coverage of the metal surface. In this case, the adsorption process is followed by electrochemical or chemical reactions of the inhibitor at the interface According to Lorenze and Mansfield,8 interface inhibition occurs in corroding systems exhibiting a bare metal surface in contact with the corrosive medium. This condition is often realized for active metal dissolution in acid solutions. Interphase inhibition presumes a three-dimensional layer between the corroding substrate and the electrolyte.7,10,11 Such layers generally consist of weakly soluble corrosion products and/or inhibitors. Interphase inhibition


Corrosion Inhibitors

57

is mainly observed in neutral media with the formation of porous or nonporous layers. Clearly, the inhibition efficiency strongly depends on the properties of the formed three-dimensional layer.

3.2 Inhibitor Evaluation Because there may be more than one inhibitor suitable for a specific application, it is necessary to have a means of comparing the performance of each. This can be done by determining the inhibitor efficiency according to the following correlation: Ieff Z

Ro KRi !100 Ro

where Ieff Z efficiency of inhibitor, %; Ro Z corrosion rate of metal without inhibitor present; Ri Z corrosion rate of metal with inhibitor present. Ro and Ri can be determined by any of the standard corrosion testing techniques. The corrosion rate can be measured in any unit, such as weight loss (mpy), as long as units are consistent across both tests.

3.3 Classification of Inhibitors Inhibitors can be classified in several ways as previously indicated. Inhibitors will be classified and discussed under the following headings: 1. Passivation inhibitors 2. Organic inhibitors 3. Precipitation inhibitors 3.3.1 Passivation Inhibitors Passivation inhibitors are chemical oxidizing materials such as chromate K ðCr2 O2K 4 Þ and nitrite ðNO2 Þ or substances such as Na3PO4 or NaBrO7. These materials favor adsorption on the metal surface of dissolved oxygen. This is the most effective and, consequently, the most widely used type of inhibitor. Chromatics are the least expensive inhibitors for use in water systems and are widely used in the recirculation-cooling systems of internal combustion engines, rectifiers, and cooling towers. Sodium chromate,


58


in concentrations of 0.04–0.1%, is used for this purpose. At higher temperatures or in freshwater that has chloride concentrations above 10 ppm, higher concentrations are required. If necessary, sodium hydroxide is added to adjust the pH to a range of 7.5–9.5. If the concentration of chromate falls below a concentration of 0.016%, corrosion will be accelerated. Therefore, it is essential that periodic colorimetric analysis be conducted to prevent this from occurring. Recent environmental regulations have been imposed on the use of chromates. They are toxic and, on prolonged contact with the skin, can cause a rash. It is usually required that the Cr6C ion be converted to Cr3C before discharge. The Cr3C ion is insoluble and can be removed as a sludge, whereas, the Cr6C ion is water-soluble and toxic. Even so, the Cr3C sludge is classified as a hazardous waste and must be constantly monitored. Because of the chromate ions’ cost of conversion, the constant monitoring required, and the disposal of the hazardous wastes, the economics of the use of these inhibitors are not as attractive as they formerly were. Because most antifreeze solutions contain methanol or ethylene glycol, the chromates cannot be used in this application because the chromates have a tendency to react with organic compounds. In these applications, borax (Na2B4O7$10H2O) that has added sulfonated oils to produce an oily coating, and mercaptobenzothiazole are used. The latter material is a specific inhibitor for the corrosion of copper. Nitrites are also used in antifreeze-type cooling water systems because they have little tendency to react with alcohols or ethylene glycol. Because they are gradually decomposed by bacteria, they are not recommended for use in cooling tower waters. Another application for nitrites is as a corrosion inhibitor of the internal surfaces of pipelines used to transport petroleum products or gasoline. Such inhibition is accomplished by continuously injecting a 5–30% sodium nitrite solution into the line. At lower temperatures, such as in underground storage tanks, gasoline can be corrosive to steel as dissolved water is released. This water, in contact with the large quantities of oxygen dissolved in the gasoline, corrodes the steel and forms large quantities of rust. The sodium nitrite enters the water phase and effectively inhibits corrosion. The nitrites are also used to inhibit corrosion by cutting oil-water emulsions used in the machining of metals. Passivation inhibitors can actually cause pitting and accelerate corrosion when concentrations fall below minimum limits. For this reason, it is essential that constant monitoring of the inhibitor concentration be performed. 3.3.2 Organic Inhibitors These materials build up a protective film of adsorbed molecules on the metal surface that provide a barrier to the dissolution of the metal in the electrolyte. Since the metal surface covered is proportional to the inhibitor concentrates, the concentration of the inhibitor in the medium is



59

critical. For any specific inhibitor in any given medium there is an optimal concentration. For example, a concentration of 0.05% sodium benzoate, or 0.2% sodium cinnamate, is effective in water that has a pH of 7.5 and contains 17 ppm sodium chloride or 0.5% by weight of ethyl octanol. The corrosion because of ethylene glycol cooling water systems can be controlled by the use of ethanolamine as an inhibitor. 3.3.3 Precipitation Inhibitors Precipitation inhibitors are compounds that cause the formation of precipitates on the surface of the metal, thereby, providing a protective film. Hard water that is high in calcium and magnesium is less corrosive than soft water because of the tendency of the salts in the hard water to precipitate on the surface of the metal and form a protective film. If the water pH is adjusted in the range of 5–6, a concentration of 10–100 ppm of sodium pyrophosphate will cause a precipitate of calcium or magnesium orthophosphate to form on the metal surface providing a protective film. The inhibition can be improved by the addition of zinc salts.

3.4 Inhibition of Acid Solution The inhibition of corrosion in acid solutions can be accomplished by the use of a variety of organic compounds. Among those used for this purpose are triple-bonded hydrocarbons; acetylenic alcohols, sulfoxides, sulfides, and mercaptans; aliphatic, aromatic, or heterocyclic compounds containing nitrogen; and many other families of simple organic compounds and of condensation products formed by the reaction between two different species such as amines and aldehydes. Incorrect choice or use of organic inhibitors in acid solutions can lead to corrosion stimulation and/or hydrogen penetration into the metal. In general, stimulation of corrosion is not related to the type and structure of the organic molecule. Stimulation of iron’s acid corrosion has been found with mercaptans, sulfoxides, azole, and triazole derivatives, nitrites, and quinoline. This adverse action depends on the type of acid. For example, bis(4-dimethylamino-phenyl) antipyrilcarbinol and its derivatives at a 10K4 M concentration inhibited attack of steel in hydrochloric acid solutions but stimulated attack in sulfuric solutions. Much work has been done studying the inhibiting and/or stimulating phenomena of organic compounds on ferrous as well as nonferrous metals. Organic inhibitors have a critical concentration value, below which inhibition ceases and stimulation begins. Therefore, it is essential that when organic inhibitors are used, constant monitoring of the solution should take place to ensure that the inhibitor concentration does not fall below the critical value.


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Generally, it is assumed that the first stage in the action mechanism of the inhibitors in aggressive acid media is adsorption of the inhibitors onto the metal surface. The process of adsorption of inhibitors is influenced by the nature and surface charge of the metal, by the chemical structure of the inhibitor, and by the type of aggressive electrolyte. Physical (or electrostatic) adsorption and chemisorption are the principal types of interaction between an organic inhibitor and a metal surface. 3.4.1 Physical Adsorption Physical adsorption is the result of electrostatic attractive forces between inhibiting organic ions or dipoles and the electrically charged surface of the metal. The surface charge of the metal is due to the electric field at the outer Helmholtz plane of the electrical double layer existing at the metal/ solution interface. The surface charge can be defined by the potential of the metal (Ecorr) vs. its zero-charge potential (ZCP) (EqZ0).12 When the difference EcorrKEqZ0Zf is negative, cation adsorption is favored. Adsorption of anions is favored when f becomes positive. This behavior is related not only to compounds with formal positive or negative charge, but also to dipoles whose orientation is determined by the value of the f potential. According to Antropov,12 at equal values of f for different metals, similar behavior of a given inhibiting species should be expected in the same environment. This has been verified for adsorption of organic charged species on mercury and iron electrodes at the same potential for both metals. In studying the adsorption of ions at the metal/solution interface, it was first assumed that ions maintained their total charge during the adsorption, giving rise in this way to a pure electrostatic bond. Lorenz13–15 suggested that a partial charge is present in the adsorption of ions; in this case, a certain amount of covalent bond in the adsorption process must be considered. The partial charge concept was studied by Vetter and Schulze,16–19 who defined as electrosorption valency the coefficient for the potential dependence and charge flow of electrosorption processes. The term electrosorption valency was chosen because of its analogy with the electrode reaction valency that enters into Faraday’s law as well as the Nernst equation. Considering the concepts discussed above in relation to corrosion inhibition, when an inhibited solution contains adsorbable anions, such as halide ions, these adsorb on the metal surface by creating oriented dipoles and, consequently, increase the adsorption of the organic cations on the dipoles. In these cases, a positive synergistic effect arises; therefore, the degree of inhibition in the presence of both adsorbable anions and inhibitor cations is higher than the sum of the individual effects. This could explain the higher inhibition efficiency of various organic inhibitors in hydrochloric acid solutions compared to sulfuric acid solutions (Table 3.1).20



61

TABLE 3.1 Inhibition Efficiency of Some Pyridinium Derivatives at the Same Molar Concentration (1!10K4 M) on Armco Iron in Hydrochloric and Sulfuric Acid Solutions at 258C Inhibition Efficiency (%) Additive n-Decylpyridinium bromide n-Decyl-3-hydroxypyridinium bromide n-Decyl-3-carboxypyridinium bromide n-Decyl-3,5-dimethylpyridinium bromide

1 N HCl

1 N H2SO4

87.6 94.8 92.7 92.5

20.0 57.5 76.5 30.2

Source: From A. Frignani, G. Trabanelli, F. Zucchi, and M. Zucchini. 1980. Proceedings of the 5th European Symposium on Corrosion Inhibitors, Ann. Univ. Ferrara, N.S., Sez. V. Suppl. 7, 1185.

3.4.2 Chemisorption Another type of metal/inhibitor interaction is chemisorption. This process involves charge sharing or charge transfer from the inhibitor molecules to the metal surface in order to form a coordinate type of bond. The chemisorption process takes place more slowly than electrostatic adsorption and with a higher activation energy. It depends on the temperature, and higher degrees of inhibition should be expected at higher temperatures. Chemisorption is specific for certain metals and is not completely reversible.22 The bonding occuring with electron transfer clearly depends on the nature of the metal and the nature of the organic inhibitor. In fact, electron transfer is typical for metals having vacant, low energy electron orbitals. Concerning inhibitors, electron transfer can be expected with compounds having relatively loosely bound electrons. This situation may arise because of the presence in the adsorbed inhibitor of multiple bonds or aromatic rings, whose electrons have a p character. Clearly, even the presence of heteroatoms with lone-pair electrons in the adsorbed molecule will favor electron transfer. Most organic inhibitors are substances with at least one functional group regarded as the reaction center for the chemisorption process. In this case, the strength of the adsorption bond is related to the heteroatom electron density and to the functional group polarizability. For example, the inhibition efficiency of homologous series of organic substances differing only in the heteroatom is usually in the following sequence: PO SeO SO NO O: An interpretation may be found in the easier polaribility and lower electronegativity of the elements on the left of the above sequence. On this basis, a surface bond of a lewis acid-base type, normally with the inhibitor


62


as the electron donor and the metal as the electron acceptor, has been postulated.21 3.4.3 Interactions between Adsorbed Inhibitors When the coverage of the metal surface by the adsorbed inhibitor species increases, lateral interactions between inhibitor molecules may arise, influencing efficiency. Attractive lateral interactions usually give rise to stronger adsorption and higher inhibition efficiency. This effect has been shown in the case of compounds containing long hydrocarbon chains, because of attractive van der Waals forces.22,23 In the presence of ions or molecules containing dipoles, repulsive interactions may occur, weakening the adsorption and diminishing the inhibiting efficiency. 3.4.4 Relationships between Inhibitor Reactivity and Efficiency The nature of the inhibitor initially present in acid solutions may change with time and/or the electrode potential as a consequence of reduction reactions, polymerization reactions, or the formation of surface products. The inhibition because of the reaction products is usually called secondary inhibition, whereas, primary inhibition is attributed to the compound initially added to the solution. Secondary inhibition may be higher or lower than primary inhibition, depending on the effectiveness of the reaction products.24 An example of inhibitors undergoing electrochemical reduction is that of sulfoxides, the most important being dibenzyl sulfoxide, whose reduction gives rise to a sulfide that is more effective than the primary compound.25 On the contrary, the reduction of thiourea and its alkyl derivatives give rise to HSK ions, whose accelerating effect is known.26 In some cases, the reduction reaction may be followed by polymerization reactions at the metal/electrolyte interface. This mechanism of action is generally accepted for acetylenic derivatives.27,28 Electrochemical measurements on iron electrodes in sulfuric acid solutions inhibited by alkynes29 showed that acetylenic compounds act as cathodic inhibitors, giving rise to a surface barrier phenomenon. Duwell et al.27 found hydrogenation and dehydration reaction products in heptane extracts of acid/iron powder/ethynylcyclohexan-1-ol. According to Duwell et al., the efficiency of ethynylcyclohexan-1-ol as a corrosion inhibitor apparently depends on the properties and rates of formation of the reaction products. Putilova et al.28 used a similar extraction technique to show that acetylene reacted at the iron/hydrochloric acid interface to form thick polymolecular films on the iron. Podobaev et al.,30 analyzing the results obtained for a large number of acetylene derivatives, concluded that these compounds act according to an adsorption-polymerization mechanism; the adsorption on iron takes place mainly via a triple bond. According to Podobaev et al.,30 the presence in the molecule of polar groups weakens



63

the stability of the triple bond and increases the probability of adsorption and polymerization. The effect of the polar groups on the triple bond reactivity is maximum when the substituent is in position 3 relative to the triple bond.

3.5 Inhibition of Near Neutral Solutions Because of the differences in the mechanisms of the corrosion process between acid and near-neutral solutions, the inhibitors used in acid solutions usually have little or no inhibition effect in near-neutral solutions. In acid solutions, the inhibition action is due to adsorption on oxide-free metal surfaces. In these media, the main cathodic process is hydrogen evolution. In almost neutral solutions, the corrosion process of metals results in the formation of sparingly soluble surface products such as oxides, hydroxides, or salts. The cathodic partial reaction is oxygen reduction. Inorganic or organic compounds as well as chelating agents are used as inhibitors in near-neutral aqueous solutions. Inorganic inhibitors can be classified according to their mechanisms of action: 1. Formation and maintenance of protective films can be accomplished by the addition of inorganic anions such as polyphosphates, phosphates, silicates, and borates. 2. Oxidizing inhibitors such as chromates and nitrites cause selfpassivation of the metallic material. It is essential that the concentration of these inhibitors be maintained above a “safe” level. If not, severe corrosion can occur as a result of pitting or localized attack caused by the oxidizer. 3. Precipitation of carbonates on the metal surfaces forming a protective film. This usually occurs because of the presence of Ca2C and Mg2C ions usually present in industrial waters. 4. Modification of surface film protective properties is accomplished by the addition of NiC2, Co2C, Zn2C, or Fe2C. The sodium salts of organic acids such as benzoate, salicylate, cinnamate, tartrate, and azelate can be used as alternatives to the inorganic inhibitors, particularly in ferrous solutions. When using these particular compounds in solutions containing certain anions such as chlorides or sulfates, the inhibitor concentration necessary for effective protection will depend on the concentration of the aggressive anions. Therefore, the critical pH value for inhibition must be considered rather than the critical concentration. Other formulations for organic inhibition of near-neutral solutions are given in Table 3.2.


64


TABLE 3.2 Organic Inhibitors for Use in Near-Neutral Solutions Inhibitor Organic phosphorus-containing compounds, salts of aminomethylenephosphonic acid, hydroxyethylidenediphosphonic acid, phosphenocarboxylic acid, polyacrylate, poly-methacrylate Borate or nitrocinnamate anions (dissolved oxygen in solution required) Acetate or benzoate anions Heterocylic compounds such as benzotriazole and its derivatives, 2-mercaptobenzothiazole, 2-mercaptobenzimidazole

Type of Metal Protected Ferrous

Zinc, zinc alloys Aluminum Copper and copperbased alloys

Chelating agents of the surface-active variety also act as efficient corrosion inhibitors when insoluble surface chelates are formed. Various surface-active chelating agents recommended for corrosion inhibition of different metals are given in Table 3.3.

3.6 Inhibition of Alkaline Solutions All metals whose hydroxides are amphoteric and metals covered by protective oxides that are broken in the presence of alkalies are subject to caustic attack. Localized attack may also occur as a result of pitting and crevice formation. Organic substances such as tannions, gelatin, saponin, and agar–agar are often used as inhibitors for the protection of aluminum, zinc, copper, and iron. Other materials that have also been found effective are thiourea, TABLE 3.3 Chelating Agents Used as Corrosion Inhibitors in Near-Neutral Solutions Chelating Agent Alkyl-catechol derivatives, sarcosine derivatives, carboxymethylated fatty amines, and mercaptocarboxylic acids Azo compounds, cupferron, and rubeanic acid Azole derivatives and alkyl esters of thioglycolic acid Oximes and quinoline derivatives Cresolphthalexon and thymolphthalexon derivatives

Type of Metal Protected Steel in industrial cooling systems Aluminum alloys Zinc and galvanized steel Copper Titanium in sulfuric acid solutions



65

substituted phenols and naphthols, b-diketones, 8-hydroxyquinoline, and quinalizarin.

3.7 Temporary Protection with Inhibitors Occasions arise when temporary protection of metallic surfaces against atmospheric corrosion is required. Typical instances are in the case of finished metallic materials or of machinery parts during transportation and/or storage prior to use. When ready for use, the surface treatment or protective layer can be easily removed. It is also possible to provide protection by controlling the aggressive gases or by introducing a vapor phase inhibitor. This latter procedure can only be accomplished in a closed environment such as sealed containers, museum showcases, or similar enclosures. Organic substances used as contact inhibitors or vapor inhibitors are compounds belonging to the following classes: 1. Aliphatic, cycloaliphatic, aromatic, and heterocyclic amines 2. Amine salts with carbonic, carbamic, acetic, benzoic, nitrous, and chromic acids 3. Organic esters 4. Nitro derivatives 5. Acetylenic alcohols

3.8 Inhibition of Localized Corrosion Corrosion inhibitors are usually able to prevent general corrosion, but their effect on localized corrosion processes is limited.31 Generally, a higher inhibitor concentration is required to prevent localized corrosion processes than is necessary to inhibit general corrosion. Staehle32 examined the possibility of inhibiting localized attack that does not depend on metallurgical structures. He considered phenomena related to: Geometric effects, such as galvanic corrosion and crevice corrosion. Simple localization of the attack, such as pitting and dezincification. Effects of relative motion, such as erosion and cavitation.

The application of organic inhibitors to control galvanic corrosion presents several problems. It is well known that an inhibitive treatment efficient on


66


a single metal, because of the specific action of the inhibitor, may fail to control corrosion if dissimilar metals are in contact. The behavior of a zincsteel couple in sodium benzoate solution was studied by Brasher and Mercer.33 Steel is protected in benzoate solution, but usually it corrodes when coupled to zinc, as in galvanized iron, in that solution. An interpretation of the phenomenon was given,33 emphasizing that rusting of steel coupled to zinc in benzoate solution can be prevented by bubbling air through the solution for one to two days immediately after immersion. After this time, the system should have become stabilized, and no corrosion of the steel should take place when the air stream is discontinued. Venezel and Wranglen34 studied the steel-copper combination in a hot-water system. The best inhibitor efficiency was obtained by using a mixture of benzoate and nitrite. It is well known35 that pitting depends not only on the concentration of aggressive anions in the solution, but also on the concentration of the nonaggressive anions. For this reason, special attention was paid to the effect of inhibitive anions in the aggressive solution. The presence of nonaggressive anions produces different effects:35 (1) shifting the pitting potential to more positive values; (2) increasing the induction period for pitting; and (3) reducing the number of pits. In studying the behavior of various anions in pitting, Strehblow36 found that pit nucleation on iron electrodes in phthalate buffer containing chloride ions was prevented by picrate ions. Strehblow and Titze37 emphasized that the pitting potential of iron in borate buffer containing chloride ions was ennobled by the presence of capronate. On the other hand, Vetter and Strahblow38 showed that sulfate ions can reduce the current density at the pit bottom area, inhibiting the propagation stage of pitting corrosion. Dezincification is the most common example of selective leaching. It is usually prevented by using less-susceptible alloys. The phenomenon can also be minimized by reducing the aggressiveness of the environment with corrosion inhibitors. Kravaeva et al.39 demonstrated that the addition of surface-active substances such as saponin, dextrin, or benzotriazole can inhibit dezincification of single-phase and diphasic brass in 0.5 N NaCl and HCl solutions. The highest inhibition efficiency was obtained by benzotriazole.

3.9 Summary Corrosion inhibitors are usually able to prevent general or uniform corrosion. However, they are very limited in their ability to prevent localized corrosion such as pitting, crevice corrosion, galvanic corrosion, dezincification, or stress corrosion cracking. Additional research work is being undertaken in the use of inhibitors to prevent these types of corrosion. The importance of these studies is realized when it is taken into account that



67

only approximately 30% of all failures because of corrosion in chemical plants result from general corrosion. The remaining 70% are due to stress corrosion cracking, corrosion fatigue, pitting, and erosion-corrosion. Attack on metals by general corrosion can be predicted and life spans of the equipment determined and/or the corrosion rates reduced by use of inhibitors. This is not the case with other types of corrosion. The use of inhibitors can be advantageous in certain cases. However, before using inhibitors, it is essential that the efficiency of the inhibitor to be used be determined to ensure that inhibition will take place.

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

17. 18. 19.

G. Trabanelli and V. Carassiti. 1970. Advances in Corrosion Science and Technology, M.G. Fontana and R.W. Staehle, Eds., Vol. 1, New York: Plenum Press, pp. 147–229. Z.A. Foroulis. 1969. Proceedings of the Symposium on Basic and Applied Corrosion Research, Houston: NACE International. O.L. Riggs, Jr. 1973. Corrosion Inhibitors, C.C. Nathan, Ed., Houston: NACE International, p. 7. J.G. Thomas. 1976. Corrosion, J.L. Shreir, Ed., 1976. Vol. 2, London: NewnesButterworths, p. 18.3. E. McCafferty. 1979. Corrosion Control by Coatings, H. Leidheiser, Ed., Princeton: Science Press, p. 279. I.L. Rosenfield. 1981. Corrosion Inhibitors, New York: McGraw-Hill. H. Fischer. 1972. Werkst. Korros., 23: 445–465. W.J. Lorenz and F. Mansfield. 1983. International Conference on Corrosion Inhibition. National Association of Corrosion Engineers, Dallas, paper 2. W.J. Lorenz and F. Mansfield. 1980. 31st ISE Meeting, Venice. P. Lorbeer and W.J. Lorenz. 1980. Electrochimica Acta, 25: 375. R.H. Hausler. 1983. International Conference on Corrosion Inhibition. National Association of Corrosion Engineers, Dallas, paper 19. L.I. Antropov. 1962. First International Congress of Metallic Corrosion, London: Butterworths, p. 147. W. Lorenz. 1962. Zeitschrift fu¨r Physikalische Chemie, 219: 421. W. Lorenz. 1963. Zeitschrift fu¨r Physikalische Chemie, 224: 145. W. Lorenz. 1970. Zeitschrift fu¨r Physikalische Chemie, 244: 65. (a) K.L. Vetter and J.W. Schulze. 1972. Berichte der Bunsengesellschaft fur Physikalische Chemie, 76: 920. (b) K.L. Vetter and J.W. Schulze. 1972. Berichte der Bunsengesellschaft fur Physikalische Chemie, 76: 927. G.W. Schulze and K.J. Vetter. 1973. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 44: 68. K.J. Vetter and J.W. Schulze. 1974. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 53: 67. (a) J.W. Schulze and K.D. Koppitz. 1976. Electrochimica Acta, 21: 327. (b) J.W. Schulze and K.D. Koppitz. 1976. Electrochimica Acta, 21: 337.


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20.

A. Frignani, G. Trabanelli, F. Zucchi, and M. Zucchini. 1980. Proceedings of the 5th European Symposium on Corrosion Inhibitors, Ann. Univ. Ferrara, N.S., Sez. V, Suppl. 7, 1185. N. Hackerman and R.M. Hurd. 1962. First International Congress on Metallic Corrosion, London: Butterworths, p. 166. T.P. Hoar and R.P. Khera. 1961. Proceedings of the 1st European Symposium on Corrosion Inhibitors, Ann. Univ. Ferrara, N.S., Sez. V, Suppl. 3, 73. N. Hackerman, D.D. Justice, and E. McCafferty. 1975. Corrosion, 31: 240. W.J. Lorenz and H. Fischer. 1969. Proceedings of the 3rd International Congress on Metals Corrosion, Vol. 2, p. 99. G. Trabanelli, F. Zucchi, G.L. Zucchini, and V. Carassiti. 1967. Electrochemicals and Methods, 2: 463. A. Frignani, G. Trabanelli, F. Zucchi, and M. Zucchini. 1975. Proceeding of the 4th European Symposium on Corrosion Inhibitors, Ann. Univ. Ferrara, N.S., Sez. V. Suppl. 6, 652. E.J. Duwell, J.W. Todd, and H.C. Butzke. 1964. Corrosion Science, 4: 435. I.N. Putflova, N.V. Rudenko, and A.N. Terentev. 1964. Russian Journal of Physical Chemistry, 38: 263. F. Zucchi, G.L. Zucchini, and G. Trabanelli. 1970. Proceedings of the 3rd European Symposium on Corrosion Inhibitors, Ann. Univ. Ferrara, N.S. Sez. V, Suppl. 5, 415. I.I. Podobaev, A.G. Voskresenkil, and G.F. Semikolenkov. 1967. Protection of Metals, 3: 88. G. Trabanelli. 1978. Proceedings of the 7th International Congress on Metallic Corrosion,. Abraçco, Rio de Janeiro, p. 83. R.W. Staehl. 1975. Proceedings of the 4th European Symposium on Corrosion Inhibitors, Ann. Univ. Ferrara, N.S. Sez. V, Suppl. 6, 709. D.M. Brasher and A.D. Mercer. 1969. Proceedings of the 3rd International Congress on Metallic Corrosion, Vol. 2, Moscow: MIR, p. 21. J. Venczel and G. Wranglen. 1967. Corrosion Science, 7: 461. S. Szklaraska-Smialowska. 1974. Localized Corrosion, Houston: NACE International, p. 329. H.H. Strehblow. 1976. Werkst. Korros., 27: 792. H.H. Strehblow and B. Titze. 1977. Corrosion Science, 17: 461. K.J. Vetter and H.H. Strehblow. 1970. Berichte der Bunsengesellschaft fur Physikalische Chemie, 74: 1024. A.P. Kravaeva, I.P. Marshakov, and S.M. Mel’nik. 1968. Protection of Metals, 4: 191.

21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39.


4 Liquid-Applied Linings

Of the various coating applications, the most critical is that of a tank lining. The coating must be resistant to the corrodent and be free of pinholes through which the corrosive could penetrate and reach the substrate. The severe attack that many corrosives have on the bare tank emphasizes the importance of using the correct procedure in lining a tank to obtain a perfect coating. It is also essential that the tank be designed and constructed in the proper manner to permit a perfect lining to be applied. Liquid-applied linings or coatings may be troweled on or spray applied. In a lined tank there are usually four areas of contact with the stored material. Each area has the potential of developing a different form of corrosive attack. These areas are the bottom of the tank (where moisture and other contaminants of greater density may settle), the liquid phase (the area constantly immersed), the interphase (the area where liquid phase meets the vapor phase), and the vapor phase (the area above the liquid). Each of these areas can be more severely attacked than the rest at one time or another. The type of material contained, the nature of impurities that may be present, and the amount of water and oxygen present are all factors affecting the attack. In view of this, it is necessary to understand the corrosion resistance of the lining material under each condition and not only the immersed condition. Other factors that have an effect on the performance of the lining material are vessel design, vessel preparation prior to lining, application techniques of the coating, curing of the coating, inspection, operating instructions, and temperature limitations. In general, the criteria for tank linings are given in Table 4.1.

4.1 Design of the Vessel All vessels to be lined internally should be of welded construction. Riveted tanks will expand or contract, thus damaging the lining and causing leakage. Butt welding is preferred, but lap welding can be used providing a fillet 69


70

Corrosion of Linings and Coatings TABLE 4.1 Criteria for Tank Linings 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Design of the vessel Lining selection Shell construction Shell preparation Lining application Cure of the lining material Inspection of the lining Safety Causes of failure Operating instructions

weld is used and all sharp edges are ground smooth (see Figure 4.1). Butt welds need not be ground flush but they must be ground smooth to a rounded contour. A good way to judge a weld is to run your finger over it. Sharp edges can be detected easily. All weld spatter must be removed (see Figure 4.2). Any sharp prominence may result in a spot where the film thickness will be inadequate and noncontinuous, thus causing premature failure. Weld

Grind smooth

Gap Inside of vessel

Inside of vessel

Round corners Continuous fillet weld

Gap

Do

Don't

FIGURE 4.1 Butt welding is preferred rather than lap welding or riveted construction.

Clean

Grind smooth Do

Weld spatter

Weld flux Don't

FIGURE 4.2 Remove all weld spatter and grind smooth.


Liquid-Applied Linings

71

If possible, avoid the use of bolted joints. Should it be necessary to use a bolted joint, it should be of corrosion-resistant materials and sealed shut. The mating surface of steel surfaces should be gasketed. The lining material should be applied prior to bolting. Do not use construction that will result in the creation of pockets or crevices that will not drain or that cannot be properly sandblasted and lined (see Figure 4.3). All joints must be continuous and solid welded. All welds must be smooth with no porosity, holes, high spots, or pockets (see Figure 4.4). All sharp angles must be ground to a minimum of 1/8 in. radius (Figure 4.5). All outlets must be of the flanged or padded type rather than threaded. If pressure requirements permit, use slip-on flanges because the inside diameter Cone or dome head Very bad, inaccessible void Shell

Skip weld Full seam weld Round corners

2 channels back to back Do

Don't

FIGURE 4.3 Avoid all pockets or crevices that cannot be properly sandblasted and lined.

Rough

Pinhole

Undercut

Grind smooth Do

Don't

FIGURE 4.4 All joints must be continuous solid welded and ground smooth.


72


Weld

Sharp corner

1/8 in. radius

Don't

Do FIGURE 4.5 Grind all sharp edges to a minimum 1/8 in. radius.

of the attaching weld is readily available for radiusing and grinding. If pressure dictates the use of weld neck flanges, the inside diameter of the attach-weld is in the throat of the nozzle. It is therefore more difficult to repair surface irregularities, such as weld undercutting by grinding (see Figure 4.6). Flanged outlet Round corners 2'' min

Pad type

2''

Weld

Weld

min

Sharp corners

Inside of vessel

Weld

Threads

Round these corners

Sharp corner

Do

Don't Nozzle lining detail

2''

Slip-on flange

I.D.

Inside of vessel

Line completely to bolt circle Full fillet weld. Grind and radius

FIGURE 4.6 Typical vessel outlets.



73 Skip weld

Inside of vessel

Inside of vessel

Angle stiffener Don't

Do FIGURE 4.7 Stiffening members should be on outside of vessel.

Stiffening members should be placed on the outside of the vessel rather than on the inside (Figure 4.7). Tanks larger than 25 ft. in diameter may require three man-ways for working entrances. Usually, two are located at the bottom, 1808 apart, and one at the top. The minimum opening is 20 in., but 30 in. openings are preferred. On occasion, an alloy is used to replace the steel bottom of the vessel. Under these conditions, galvanic corrosion will take place. If a lining is applied to the steel and for several inches, usually 6–8 in. onto the alloy, any discontinuity in the lining will become anodic. After corrosion starts, it progresses rapidly because of the bare alloy cathodic area. Without the lining, galvanic corrosion would cause the steel to corrode at the weld area, but at a much lower rate. The recommended practice, therefore, is to line the alloy completely as well as the steel, thereby eliminating the possible occurrence of a large cathode to small anode area (see Figure 4.8).

Pit (anode) Steel

Protective coating Alloy (cathode)

FIGURE 4.8 Potential galvanic action.


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It is important that processing liquor is not directed against the side of the vessel, but rather toward the center. Other appurtenances inside the vessel must be located for accessibility of the lining. Heating elements should be placed with a minimum clearance of 6 in. Baffels, agitator base plates, pipes, ladders, and other items can either be lined in place or detached and coated before installation. The use of complex shapes such as angle channels and I-beams should be avoided. Sharp edges should be ground smooth and should be fully welded. Spot welding or intermittent welding should not be allowed. Gouges, hackles, deep scratches, slivered steel, or other surface flaws should be ground smooth. Concrete tanks should be located above the water table. They require special lining systems. Unless absolutely necessary, expansion joints should be avoided. Small tanks do not normally require expansion joints. Larger tanks can make use of a chemically-resistant joint such as a polyvinyl chloride (PVC). Any concrete curing compound must be compatible with the lining material, or removed before application. Form joints must be as smooth as possible. Adequate steel reinforcement must be used in a strong, dense concrete mix to reduce movement and cracking. The lining manufacturer should be consulted for special instructions. Concrete tanks should be coated by a licensed applicator.

4.2 Vessel Preparation For the lining material to obtain maximum adhesion to the substrate surface, it is essential that the surface be absolutely clean. All steel surfaces to be coated must be abrasive-blasted to a white metal in accordance with SSPC Specification SP5-63 or NACE Specification 1. A white metal blast is defined as removing all rust, scales, paints, and so on, to a clean white metal that has a uniform gray-white appearance. No streaks or stains of rust or any other contaminants are allowed. At times, a near-white, blast-cleaned surface equal to SSPC SP-10 may be used. If this is permitted by the manufacturer of the lining material it should be used as it is less expensive. All dust and spent abrasive must be removed from the surface by vacuum cleaning or brushing. After blasting, all workers coming into contact with the clean surface should wear clean, protective gloves and clothing to prevent contamination of the cleaned surface. Any contamination may cause premature failure by osmotic blistering or adhesion loss. The first coat must be applied before the surface starts to rust. Concrete surfaces must be clean, dry, and properly cured before applying the lining. All protrusions and form joints must be removed. All surfaces must be toughened by sandblasting to remove all loose, weak, or powdery concrete to open all voids and provide the necessary profile for mechanical adhesion of the coating. All dust must be removed by brushing or



75

vacuuming. The coating manufacturer should be contacted for special priming and caulking methods.

4.3 Lining Function The primary function of a coating system is to protect the substrate. An equally important consideration is product purity protection. The purity of the liquid must not be contaminated with byproducts of corrosion or leachate from the lining system itself. Selection of a lining material for a stationary storage tank dedicated to holding one product at more or less constant durations and temperatures is relatively easy because such tanks present predictable conditions for coating selection. Conversely, tanks that see intermittent storage of a variety of chemicals or solvents, such as product carriers, present a more difficult problem because the parameters of operation vary. Consideration must be given to the effect of cumulative cargoes. In addition, abrasion resistance must be considered if the product in the tank is changed regularly. With complete cleaning between loads, the coating will be abraded.

4.4 Lining Selection To properly specify a lining material, it is necessary to know specifically what is being handled and under what conditions. The following information must be known about the material being handled: 1. What are the primary chemicals to be handled and at what concentrations? 2. Are there any secondary chemicals, and if so at what concentrations? 3. Are there any trace impurities or chemicals? 4. Are there any solids present, and if so what are the particle sizes and concentrations? 5. Will there be any agitation? 6. What are the fluid purity requirements? 7. What will be present in the vapor phase above the liquid? The answers to these questions will narrow the selection to those coatings that are compatible. Table 4.2 provides a list of typical lining materials and their general area of application. However, the answers to the next set of questions will narrow the selection down to those materials that are


76


TABLE 4.2 Typical Lining Materials Lining Material

Applications

High-bake phenolic

Excellent resistance to acids, solvents, food products, beverages and water. Most widely used lining material, but has poor flexibility compared with other lining materials. Nearly equal in resistance to high-bake phenolics. May be formulated for excellent resistance to alkalies, solvents, salt water, deionized water, fresh water, and mild acids. Excellent for dry products. Excellent resistance to strong mineral acids and water. Most popular lining for water storage tanks; used in water immersion service (potable and marine) and beverage processing. Acid resistant; must be heat cured. Chemical salts. Good alkali resistance. Fair to good resistance to solvents, mild acids, and dry food products. Finds application in covered hopper-car linings and nuclear containment facilities. Good resistance to water and brines. Used in storage tanks and nuclear containment facilities. Poor acid resistance and fair alkali resistance. Good abrasion resistance. Used for covered hopper-car linings. Poor solvent resistance. Excellent resistance to mild acids, mild alkalies, salt water, and fresh water. Poor solvent resistance. Used for crude oil storage tanks, sewage disposal plants, and water works. Excellent water resistance. Used for water tanks. Good acid and water resistance. Good acid and flame resistance. Used for chemical processing equipment. Good water and solvent resistance. Good water resistance. Finds application in food and beverage processing and in the lining of concrete tanks. Excellent alkali resistance. Finds application in caustic tanks (50–73%) at 1808F (828C) to 2508F (1218C). Superior abrasion resistance. Excellent resistance to strong mineral acids and alkalies. Fair solvent resistance. Used to line dishwashers and washing machines. Excellent resistance to strong acids and better resistance up to 3508F (1938C) to 4008F (2048C), depending upon thickness. Finds application in food processing, hopper cars, and wood tanks. High chemical resistance and fire resistance. Used in SO2 scrubber service. Excellent fuel oil resistance.

Modified air-dry phenolics (catalyst required) Modified PVC polyvinyl chloroacetals, air-cured PVC plastisols Hypalon Epoxy (amine catalyst) Epoxy polyamide Epoxy polyester Epoxy coal tar Coal tar Asphalts Neoprene Polysulfide Butyl rubber Styrene-butadiene polymers Rubber latex Urethanes Vinyl ester Vinyl urethanes Fluoropolymers Vinylidene chloride latex Alkyds, epoxy esters, oleoresinous primers

Water immersion applications and as primers for other top coats.

(continued)



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TABLE 4.2 Continued Lining Material Inorganic zinc, water-based postcure, and waterbased self-cure Inorganic zinc, solvent-based self-curing Furan

Applications Jet fuel storage tanks and petroleum products.

Excellent resistance to most organic solvents (aromatics, ketones, and hydrocarbons), excellent water resistance. Difficult to clean. May be sensitive to decomposition products of materials stored in tanks. Most acid resistant organic polymer. Used for stack linings and chemical treatment tanks.

compatible as well as to those coatings that have the required mechanical and/or physical properties. 1. What is the normal operating temperature and temperature range? 2. What peak temperatures can be reached during shutdown, startup, process upset, etc.? 3. Will any mixing areas exist where exothermic or heat of mixing temperatures may develop? 4. What is the normal operating pressure? 5. What vacuum conditions and range are possible during operation, startup, shutdown, and upset conditions? 6. Is grounding necessary? Other factors must also be considered before the final decisions can be made as to which coating to use. After the previous questions have been answered, there will still be several potential materials from which to choose. Service-life expectation must be considered. Different protective coating options afford different degrees of protection for different periods of time at a variety of costs. Factors such as maintenance cycle, operating cycles, and reliability of the coating must all be considered. Can the facility tolerate any downtime for inspection and maintenance? If so, how often and for how long? When these questions have all been answered, an appropriate decision can be made as to which coating material will be used. The size of the vessel must also be considered in the coating selection. If the vessel is too large, it may not fit in a particular vender’s oven for curing the coating. Also, nozzle diameters 4 in. or less are too small to spray-apply a liquid coating. When a lining is to be used for corrosion protection, it is necessary to review the corrosion rate of the immersed environment on the bare substrate. Assuming that the substrate is carbon steel with a corrosion rate of less than 10 mil per year (mpy) at the operating temperature, pressure,


78


and concentration of corrodent, then a thin film lining of less than 20 mil can be used. For general corrosion, this corrosion rate is not considered severe. However, if a pinhole should be present through the lining, a concentration of the corrosion current density occurs as a result of the large ratio of cathode area to anode area. The pitting corrosion rate will rapidly increase above the 20 mpy rate and through-wall penetration can occur in months. When the substrate exhibits a corrosion rate in excess of 10–20 mpy, a thick film coating exceeding 20 mil in thickness is used. These thicknesses are less susceptible to pinholes. Thin linings are used for overall corrosion protection as well as combating localized corrosion such as pitting and stress cracking of the substrate. Thin fluoropolymer coatings are used to protect purity and to provide nonstick surfaces for easy cleaning. Among the materials available for thin coatings are those based on epoxy and phenolic resins that are 0.15–0.30 mm (0.006–0.12 in.) thick. They are either chemically cured or heat baked. Baked phenolic linings are used to protect railroad tank cars transporting sulfonic acid. Tanks used to store caustic soda (sodium hydroxide) have a polyamide cured epoxy coating. Thin coatings of sprayed and baked FEP, PFA, and ETFE are also widely used. They are applied to primed surfaces as sprayed water-borne suspension or electrostatically charged powders sprayed on a hot surface. Each coat is baked before the next is applied. Other fluoropolymers can also be susceptible to delamination in applications where temperatures cycle frequently between ambient and steam. Table 4.3 presents details of these linings. Fluoropolymer thin coatings can be applied as thick coatings. When the corrosion rate of the substrate exceeds 10-mpy-thick coatings exceeding 2.5 mil (0.025 in.) are recommended. One such coating is vinyl ester reinforced with glass cloth or woven roving. Coatings greater than 125 mil (0.125 in.) thick can be sprayed or troweled. Maximum service temperature is 1708F (738C). These coatings can be applied in the field and are used in service with acids and some organics. Another thick coating material for service with many acids and bases is plasticized PVC. This has a maximum operating temperature of 1508F (668C). Sprayed and baked electrostatic powder coating of fluoropolymers, described under thin coatings, can also be applied as thick coatings. One such coating is PVDF and glass or cotton fabric. Manufacturers and/or other corrosion engineers should be consulted for case histories of identical applications. Included in the case history should be the name of the applicator who applied the coating, application conditions, type of equipment used, degree of application difficulty, and other required special procedures. A lining with superior chemical resistance will fail rapidly if it cannot be properly applied, so it is advantageous to learn from the experience of others. To maximize sales, lining manufacturers formulate their products to meet as broad a range as possible of chemical and solvent environments. Consequently, a tank coating may be listed as suitable for more than 100


0.04 (1.0) 0.01–0.04 (0.25–1.0) 0.025–0.03 (0.06–0.76) 0.08 (2.0)

Thickness, in. (mm)

PFA with mesh and carbon PVDF with 0.04–0.09 (1.0–2.30) mesh and carbon Electrostatic Spray Powders ETFE Up to 0.09 (2.3) FEP 0.01–(0.28) PFA 0.01 (0.28) ECTFE 0.06–0.07 (1.5–1.8) PVDF 0.025 (0.64)

PVDF

Sprayed Dispersions FEP PFA

Lining System

Fluoropolymer Lining Systems

TABLE 4.3

Hot patching is possible, but testing is recommended Hot patching is possible, but testing is recommended

Primer and multiple coats applied with electrostatic spraying equipment. Each coat is baked

Pressure allowed. Vacuum rating undetermined

8 ft. (2.4 m) dia. 40 ft. (12.2 m) length

Repair Considerations

Primer and multiple coats with combination 2 psig equipment. Each coat is baked

Installation

Pressure allowed. Vacuum rating undetermined

Design Limits

8 ft. (2.4 m) dia. 40 ft. (12.2 m) length

Maximum Size

Liquid-Applied Linings 79


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products with varying degrees of compatibility. However, there is potential danger of failure if the list is viewed only from the standpoint of the products approved for service. If more than one of these materials listed as being compatible with the lining is to be used, consideration must be given to the sequence of use in which the chemicals or solvents will be stored or carried in the tank. This is particularly critical when the cargo is water miscible, for example methanol or cellosolve, and is followed by a water ballast. A sequence such as this creates excessive softening of the film and makes recovery of the lining film more difficult and thus prone to early failure. Certain tank coating systems may have excellent resistance to specific chemicals for a given period after which they must be cleaned and allowed to recover for a designated period of time to return to their original resistance level. Thirty days is a common period of time for this process between chemicals such as acrylonitrile and solvents such as methanol. When case histories are unavailable, or manufacturers are unable to make a recommendation, it will be necessary to conduct tests. This can occur in the case of a proprietary material being handled or if a solution might contain unknown chemicals. Sample panels of several coating systems should be tested for a minimum of 90 days, with a 6 month test being preferable. Because of time requirements, 90 days is standard. The test must be conducted at the maximum operating temperature to which the lining will be subjected and should simulate operating conditions, including washing cycles, cold wall, and the effects of insulation. Other factors to consider in lining selection include service life, maintenance cycles, operating cycles, and the reliability of the lining. Different protective linings provide different degrees of protection for various periods of time, at a variety of costs. Allowable downtime of the facility for inspection and maintenance must also be considered in terms of frequency and length of time. After the coating system has been selected, recommendations from the manufacturer for a competent applicator should be requested and contact should made with previous customers.

4.5 Lining Application In lining a vessel, the primary concern is to deposit a void-free film of the specified thickness on the surface. Any area that is considerably less than the specified thickness may have a noncontinuous film. In addition, pinholes in the coating may cause premature failure. If the film is too thick, there is always the danger of solvents being entrapped, which can lead to bad adhesion, excessive brittleness, improper cure, and subsequent poor performance. Dry spraying of the coating should be avoided because it causes the coating to be porous. Poor film formation may be caused if thinners other than those recommended by the coating



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manufacturer are used. Do not permit application to take place below the temperature recommended by the manufacturer. During application, the film thickness should be checked. This can be accomplished by use of an Elcometer or Nordsen wet film thickness gauge. If the wet film thickness meets specifications, in all probability the dry film will also be within specification limits. All gauges used to measure dry film thickness must be calibrated before use, following the manufacturer’s recommended procedure. Readings should be taken at random locations on a frequent basis. Special attention should be given to hard-to-coat areas.

4.6 Inspection Proper inspection requires that the inspector be involved with the job from the beginning. An understanding of the design criteria of the vessel and the reasons for the specific design configuration is helpful. The inspector should participate in the prework meeting, prejob inspection, surface preparation inspection, and coating application inspection. Daily inspection reports should be prepared along with a final acceptance report. Before the coating is applied, the inspector should verify that the vessel has been properly prepared for lining. Welds must be ground smooth with a rounded contour. It is not necessary that they be ground flush. Sharp protrusions should be rounded and weld crevices manually opened so that the coating can penetrate. If this is not possible, the projection should be removed by grinding. Back-to-back angles, tape, or stitch welding cannot be properly cleaned and coated. They should be sealed with caulking to prevent crevice corrosion. After the vessel has been sandblasted, the inspector should work quickly so that the application of the coating to the surface is not delayed. The inspector should examine coatings during and after application. It is important to check for porosities. The first visual inspection is mandatory to detect pinholing and provide recoat instructions. Visual inspections are performed either with the unaided eye or by the use of a magnifying glass. After repairs of visible defects, inspection should be carried out using low voltage (75 V or less) holiday detectors that ring, buzz, or light up to show electrical contact through a porosity within the coating to the metal surface. This check should be performed after the primer or second coat, so that these areas can be touched up and made free of porosities before the final top coat. These visual techniques permit the inspector to identify areas that have been missed, damaged areas, or thin areas. In some instances, white primers have been used to spot areas of low film thickness or inadequate coverage of the substrate. The final test, employing instruments, will provide the inspector with an accurate appraisal as to whether or not the proper film thickness has been achieved.


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The inspector should also be involved in the selection of the applicator. Because a tank lining requires nearly perfect application, a knowledgeable and conscientious contractor is required. Again, the lowest bidder is not necessarily the best choice. Evaluate the applicator before awarding the contract to assure that the tank lining contractor is experienced in applying the specified lining. Before placing a contractor on the bidder’s list, review his qualifications. Inquire as to what jobs he has done using the selected lining material and follow up with those particular applications. If possible, visit his facilities and inspect his workmanship. An experienced inspector is helpful during this evaluation. Taking these steps will help ensure installation of a tank lining that will provide the desired performance.

4.7 Curing Proper curing is essential if the lining is to provide the corrosion protection for which it was selected. Each coat must be cured using proper air circulation techniques. Fresh air over 508F (108C) and having a relative humidity of less than 89% should be supplied to an opening at the top of the vessel with an exhaust at the bottom. The air flow should be fed by forced air fans and should be downward because the solvents used in coatings are usually heavier than air. Because of this, proper exhaustion can only be obtained with downward flow. To prevent solvent entrapment between coats and to ensure a proper final cure, the curing time and temperature must be in accordance with the manufacturer’s instructions for the specific coating material. A warm forcedair cure between coats and as a final cure will provide a dense film and tighter cross-linking, which provides superior resistance to solvents and moisture permeability. Before placing the vessel in service, the lining should be washed down with water to remove any loose overspray. Linings must be allowed sufficient time to obtain a full cure before being placed in service. This usually requires 3–7 days. Do not skimp on this time. When the tank is placed in service, operating instructions should be prepared and should include the maximum temperature to be used. The outside of the tank should be labeled; “Do not exceed X8F (X8C). This tank has been lined with___________. It is to be used only for ___________ service.”

4.8 Safety during Application Many lining formulations contain solvents, making it necessary to take certain safety precautions. It is necessary that all lining materials and thinners be kept away from any source of open flame. This means that welding in



83

adjacent areas must be discontinued during application and “no smoking” must be the rule during application. A power air supply and ventilation must be provided during the application of the lining. The vapor concentration inside of the vessel should be checked on a regular basis to ensure that the maximum allowable vapor concentration is not reached. For most solvents, a vapor concentration of between 2% and 12% in the air is sufficient to cause an explosion. As long as the vapor concentration is kept below the lower level, no explosion will take place. All electrical equipment must be grounded. Because flammable solvents are being exhausted from the tank, precautions must be taken on the exterior of the tank. These flammable vapors will travel a considerable distance along the ground. No flames, sparks, or ungrounded equipment can be nearby. Those applying the lining should wear fresh airline respirators and protective cream on exposed parts of the body. Water should be available for flushing accidental spills on the skin. Never allow one worker in the tank alone. OSHA issues a form called the Material Data Sheet. The manufacturers supply this form by listing all toxicants or hazardous materials and provide a list of the solvents used. Also included are the threshold limit values (TLVs) for each substance. Explosive hazards, flash points, and temperature limits are established for safe application of each lining material. These Material Safety Data Sheets should be kept on file in the job superintendents office and at the first aid station.

4.9 Causes of Lining Failure Most lining failures are the result of the misuse of the tank lining, which results in blistering, cracking, hardening or softening, peeling, staining, burning, and undercutting. A frequent cause of failure is overheating during operation. When a heavily pigmented surface or thick film begins to shrink, stresses are formed on the surface that result in cracks. These cracks do not always expose the substrate and may not penetrate. Under these conditions, the best practice is to remove these areas and recoat according to standard repair procedures. Aging or poor resistance to the corrosive can result in hardening or softening. As the coating ages, particularly epoxy and phenolic amines, it becomes brittle and may chip from the surface. Peeling can result from improperly cured surfaces, poor surface preparation, or a wet or dry surface. Staining results when there is a reaction of the corrosive on the surface of the lining or slight staining from impurities in the corrosive. The true cause must be determined by scraping or detergent washing the lining. If the stain is removed and softening of the film is not apparent, failure has not occurred.


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Any of the above defects can result in undercutting. After the corrosive penetrates to the substrate, corrosion will proceed to extend under the film areas that have not been penetrated or have not failed. Some linings are more resistant than others to undercutting or underfilm corrosion. Usually, if the lining exhibits good adhesive properties, and if the primer coat is chemically-resistant to the corrosive environment, underfilm corrosion will be greatly retarded. In addition, a tank lining must not impart any impurities to the material contained within it. The application is a failure if any taste, smell, color, or other contamination is imparted to the product, even if the lining is intact. Such contamination can be caused by the extraction of impurities from the lining, leading to blistering between coats to the metal. If the lining is unsuited to the service, complete failure may occur by softening, dissolution, and finally complete disintegration of the lining. This type of problem is prevalent between the interphase and bottom of the tank. At the bottom of the tank and throughout the liquid phase, penetration is of great concern. The vapor phase of the tank is subject to corrosion from concentrated vapors mixed with any oxygen present and can cause extensive corrosion.

4.10 Specific Liquid Linings Most liquid-applied lining materials are capable of being formulated to meet requirements for specific applications. Corrosion data referring to the suitability of a lining material for a specific corrodent indicates that a formulation is available to meet these conditions. Because all formulations may not be suitable, the manufacturer must be checked as to the suitability of his formulation. The most common linings are discussed. 4.10.1 Phenolics Synthetic phenolic resins were developed and commercialized in the early 1900s by Leo Bakeland.2 The reduction of phenol and formaldehyde produces a product that forms a highly cross-linked, three-dimensional product when cured. The resins have found use in various applications in the lining industry because of their excellent heat resistance, chemical resistance, and electrical properties. They also offer good adhesion to many substrates and have good compatibility with other polymers. Phenolic resins have two basic classifications: resoles and novalaks. Resoles, or heat reactive resins, are made using an excess of formaldehyde and a base catalyst. The polymer that is produced has reactive methylol groups that form a thermoset structure when heat is applied. Novalaks are made using an excess of phenol and an acid catalyst. Reaction occurs by the protonation of formaldehyde,3 and the intermediate



85

is characterized by methylene linkages rather than methylol groups. These products are not heat reactive and require additional cross-linking agents such as hexamethylenetetramine to become thermosetting. Both polymerization reactions evolve water during curing. This condensation reaction serves to limit film thicknesses to approximately 3 mil because the volatiles will cause blistering while curing takes place. The outstanding phenolic systems are those that are baked at approximately 4508F (2308C) to provide a 3–5 mil (75–130 mm) lining of high chemical resistance. Phenolic coatings have a wet temperature resistance to 2008F (938C). They are odorless, tasteless, nontoxic, and suitable for food use. They must be baked at a metal temperature ranging from 350 to 4508F (175–2308C). The coating must be applied in a thin layer (approximately 1 mil (0.03 mm)) and partially baked between coats. Multiple thin coats are necessary to allow removal of water from the condensation reaction. The cured coating is difficult to patch due to extreme solvent resistance. A brown color results upon baking that can be used to indicate the degree of cross-linking. It can be modified with epoxies and other resins to enhance water, chemical, and heat resistance. Phenolic resins exhibit excellent resistance to most organic solvents, especially aromatic and chlorinated solvents. Organic polar solvents capable of bonding, such as alcohols and ketones, can attack phenolics. Although the phenolics have an aromatic character, the phenolic hydroxyls provide sites for hydrogen bonding and attack by caustics. Phenolics are not suitable for use in strong alkaline environments. Strong mineral acids also attack the phenolics, and acids such as nitric, chromic, and hydrochloric can cause severe degradation. Sulfuric and phosphoric acids may be suitable under some conditions. There is some loss of properties when phenolics are in contact with organic acids such as acetic, formic, or oxalic. Although attacked by oxidants and even by dilute alkalies, the phenolics provide both corrosion and contamination protection in a wide variety of chemical and petroleum services. Refer to Table 4.4 for the compatibility of phenolics with selected corrodents. Modified air-dried phenolics are nearly equivalent to high-baked phenolics with a dry heat resistance of 1508F (658C). They can be formulated for excellent resistance to alkalies, solvents, fresh water, salt water, deionized water, and mild acid resistance. 4.10.2 Epoxy Epoxy resins can be formulated with a wide range of properties. These medium to high-priced resins are noted for their adhesion. Epoxy linings provide excellent chemical and corrosion resistance. They exhibit good resistance to alkalies, non-oxidizing acids, and many solvents. Typically


86


epoxies are compatible with the following materials at 2008F (938C) unless otherwise noted: Acids

Acetic, 10% to 1508F (668C) Butyric Hydrochloric, 10% Rayon spin bath Sodium hydroxide, 50% to 1808F (828C) Trisodium phosphate

Salts, Metallic salts

Aluminum Iron Potassium Most ammonium salts Methyl Ethyl Isopropyl, to 1508F (668C) Benzene, to 1508F (668C) Distilled water Jet fuel White liquor Sour crude oil Bromine water Bleaches Methylene chloride Sulfuric acid above 70% Wet sulfur dioxide

Bases

Alcohols, Solvents

Miscellaneous

Benzoic Fatty acids Oxalic Sulfuric, 20% to 1808F (828C) Sodium sulfide, 10% Magnesium hydroxide Calcium Magnesium Sodium

Ethyl acetate, to 1508F (668C) Naphtha Toluene Xylene Sea water Gasoline Diesel fuel Black liquor

Epoxies are not satisfactory for use with: Chromic acid Fluorine Hydrogen peroxide Wet chlorine gas

Refer to Table 4.5 for the compatibility of epoxy with selected corrodents, and Reference [1] for a more comprehensive listing. Epoxy resins must be cured with cross-linking agents (hardeners) or catalysts to develop the desired properties. Cross-linking takes place at the epoxy and hydroxyl groups that are the reaction sites. The primary types of curing agents used for linings are the aliphatic amines and catalytic curing agents. Epoxies (amine catalyst) are widely used because curing of the epoxies takes place at room temperature. High exothermic reactions develop during the curing reaction, which limits the mass of material that can be cured. Amine-cured coatings exhibit good resistance to alkalies, and fair to good resistance to mild acids, solvents, and dry food products. They are widely used for hopper car linings and nuclear containment facilities. The maximum allowable temperature is 2758F (1358C). Catalytic curing agents require a temperature of 2008F (938C) or higher to react. These baked epoxies exhibit excellent to acids, alkalies, solvents,



87

TABLE 4.4 Compatibility of Phenolics with Selected Corrodents Maximum Temperature Chemical Acetic acid, 10% Acetic acid, glacial Acetic anhydride Acetone Aluminum chloride, aqueous Aluminum sulfate Ammonia gas Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium sulfate, 10–40% Aniline Benzaldehyde Benzene Benzenesulfonic acid, 10% Benzoic acid Benzyl alcohol Butadiene Butyl phthalate Calcium chlorate Calcium hypochlorite, 10% Carbon dioxide, dry Carbon dioxide, wet Carbon tetrachloride Carbonic acid Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chromic acid, 50% Chromyl chloride Citric acid, conc. Copper acetate Cresol Ethylene glycol Ferric chloride, 50% in water Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrofluoric acid, 30%

8F

8C

212 70 70 X 90 300 90 90 80 80 80 X X 160 300 X 70 160 70

100 21 21 X 32 149 32 32 27 27 27 X X 71 149 X 21 71 21

70 X 160 300 X 300 300 200 200 X X 260 160 X X 160 160 300 70 300 200 200 200 300 300 X

21 X 71 149 X 149 149 93 93 X X 127 71 X X 71 71 149 21 149 93 93 93 149 149 X (continued)


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Corrosion of Linings and Coatings TABLE 4.4 Continued Maximum Temperature Chemical Hydrofluoric acid, 60% Hydrofluoric acid, 100% Lactic acid, 25% Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Phosphoric acid, 50–80% Picric acid Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 15% Sodium hypochlorite, conc. Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfurous acid Thionyl chloride Zinc chloride

8F

8C

X X 160 160 X 160 300 X X X X X 212 300 X X X X 250 250 200 70 X X 80 200 300

X X 71 71 X 71 149 X X X X X 100 149 X X X X 121 121 93 21 X X 27 93 149

The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. A blank space indicates that data is unavailable. Source: From P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.

inorganic salts, and water. The maximum operating temperature is 3258F (1638C), somewhat higher than that of the amine-cured epoxies. 4.10.3 Furans Furan polymers are derivatives of furfuryl alcohol and furfural.4 Using an acid catalyst, polymerization occurs by the condensation route that generates heat and water by-product. All furan linings must be post-cured to drive out the reaction “condensate” to achieve optimum properties.



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TABLE 4.5 Compatibility of Epoxy with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aq. 1% Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonia gas, dry Ammonium bifluoride Ammonium carbonate Ammonium chloride, sat. Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate, 25% Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium sulfide Barium chloride Barium hydroxide, 10% Barium sulfate Benzaldehyde Benzene Benzenesulfonic acid, 10% Benzoic acid Benzyl alcohol

8F

8C

150 90 190 110 110 X 110 X X 90 250 X 140 300 300 90 180 180 250 300 210 90 140 180 150 140 150 250 250 140 300 100 80 140 80 150 180 X 240 300 250 200 250 X 160 160 200 X

66 32 88 43 43 X 43 X X 32 121 X 60 149 149 32 82 82 121 149 99 32 60 82 66 60 66 121 121 60 149 38 27 60 27 66 82 X 116 149 121 93 121 X 71 71 93 X

(continued)


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Corrosion of Linings and Coatings TABLE 4.5 Continued Maximum Temperature Chemical Benzyl chloride Borax Boric acid, 4% Bromine gas, dry Bromine gas, moist Bromine, liquid Butadiene Butyl acetate Butyl alcohol n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride, 37.5% Calcium hydroxide, sat. Calcium hypochlorite, 70% Calcium nitrate Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloroacetic acid, 92% water Chloroacetic acid Chlorine gas, dry Chlorine gas, wet Chlorobenzene Chromic acid, 50% Chloroform Chlorosulfonic acid Chromic acid, 10% Citric acid, 15% Citric acid, 32% Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate, 17% Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid

8F

8C

60 250 200 X X X 100 170 140 X 210

16 121 93 X X X 38 77 60 X 99

200 300 200 190 180 150 250 250 X 100 200 100 80 170 200 140 150 X 150 X 150 X 110 X 110 190 190 200 150 250 150 210 100 80 80 90 80 X

93 149 93 88 82 66 121 121 X 38 93 38 27 77 93 60 66 X 66 X 66 X 43 X 43 88 88 93 66 121 66 99 38 27 27 32 27 X

(continued)



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TABLE 4.5 Continued Maximum Temperature Chemical Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 10% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50%

8F

8C

X 300 300 250 250 250

X 149 149 121 121 121

90 180 180 110 200 140 160 X X X 200 X 220 200 190 X 90 140 140 160 100 X X X X 90 80 X 110 80 200 140 300 210 190 200 X X 250 200 160 140 110

32 82 82 43 93 60 71 X X X 93 X 104 93 88 X 32 60 60 71 38 X X X X 32 27 X 43 27 93 60 149 99 88 93 X X 121 93 71 60 43

(continued)


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Corrosion of Linings and Coatings TABLE 4.5 Continued Maximum Temperature Chemical Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid, 20% Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

8F

8C

110 X X X X 240 X 150 X 90 250

43 X X X X 116 X 66 X 32 121

The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. A blank space indicates that the data is unavailable. Source: From P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.

Furan polymers are noted for their excellent resistance to solvents and they exhibit excellent resistance to strong concentrated mineral acids, caustics, and combinations of solvents with acids and bases. These furans are subject to many different formulations, making them suitable for specific applications. Consequently, the manufacturer should be consulted for the correct formulation for a specific application. In general, furan formulations are compatible with the following: Acetone Chlorobenzene Methanol Styrene Xylene

Solvents Benzene Ethanol Methyl ethyl ketone Trichloroethylene Carbon disulfide

Diethylamine Sodium sulfide

Acids Hydrochloric Sulfuric, 60% to 1508F (668C) Bases Sodium carbonate Sodium hydroxide, 50%

Demineralized

Distilled

Acetic Phosphoric

Pulp mill liquor

Ethyl acetate Perchloroethylene Toluene

Nitric, 5%

Water Others



93

The furan resins are not satisfactory for use with oxidizing media, such as chromic or nitric acids, peroxides, hypochlorites, chlorine, phenol, and concentrated sulfuric acid. Refer to Table 4.6 for the compatibility of furan resins with selected corrodents and Reference [1] for a more complete listing. 4.10.4 Vinyl Esters The vinyl ester class of resins was developed during the late 1950s and early 1960s. Vinyl esters were first used as dental fillings. They had improved toughness and bonding ability over the acrylic materials that were being used at that time. Over the next several years, changes in the molecular structure of the vinyl esters produced resins that found extensive use in corrosion-resistant equipment. Present-day vinyl esters possess several advantages over unsaturated polyesters. They provide toughness in the cured polymer while maintaining good thermal stability and physical properties at elevated temperatures. Vinyl esters are available in various formulations. Halogenated modifications are available where fire resistance and ignition resistance are major concerns. The vinyl esters are resistant up to 4008F (2048C). Vinyl esters can be used to handle most hot, highly chlorinated and acid mixtures at elevated temperatures. They also provide excellent resistance to strong mineral acids and bleaching solutions. Vinyl esters excel in alkaline and bleach environments and are used extensively in the very corrosive conditions found in the pulp and paper industry. The family of vinyl esters includes a wide variety of formulations. As a result, there can be differences in the compatibility in a reference table. One must keep in mind that all formulations will not act as shown. An indication that a vinyl ester is compatible generally means that at least one formulation is compatible. This is the case in Table 4.7 which shows the compatibility of vinyl ester with selected corrodents. The resin manufacturer must be consulted to verify the resistance. 4.10.5 Epoxy Polyamide Polyamide resins (nylons) can react with epoxies to form durable protective linings with a temperature resistance of 2258F (1078C) dry and 1508F (668C) wet. The chemical resistance of the polyamides is inferior to that of the amine-cured epoxies. They are partially resistant to acids, acid salts, alkaline and organic solvents, and are resistant to moisture. Refer to Table 4.8 for the compatibility of epoxy polyamides with selected corrodents and to Reference [1] for a more complete listing. Applications include storage tanks and nuclear containment facilities.


94

Corrosion of Linings and Coatings TABLE 4.6 Compatibility of Furans with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid, 25% Allyl alcohol Allyl chloride Alum, 5% Aluminum chloride, aq. Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum sulfate Ammonium carbonate Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfide Benzaldehyde Benzene Benzenesulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry

8F

8C

X 212 160 80 80 80 80 200 80 80 280 300 300 140 300 300 280 260 160 240 250 200 250 260 260 260 260 240 260 278 X 80 250 X 240 260 260 260 80 160 160 260 80 140 140 300 X

X 100 71 27 27 27 27 93 27 27 138 149 149 60 149 149 138 127 71 116 121 93 121 127 127 127 127 116 127 137 X 27 121 X 116 127 127 127 27 71 71 127 27 60 60 149 X (continued)



95

TABLE 4.6 Continued Maximum Temperature Chemical Bromine gas, moist Bromine, liquid, 3% max Butadiene Butyl acetate Butyl alcohol n-Butylamine Butyric acid Calcium bisulfite Calcium chloride Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon tetrachloride Cellosolve Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chloroacetic acid Chloroacetic acid, 50% water Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride

8F

8C

X 300

X 149

260 212 X 260 260 160 260 X 260

127 100 X 127 127 71 127 X 127

260 250 160 90 80 260 212 240 260 260 X 240 100 260 X 260 X X 250 250 250 260

127 121 71 32 27 127 100 116 127 127 X 116 38 127 X 127 X X 121 121 121 127

260 240 300 260 300 300 140

127 116 149 127 149 149 60

X 250 160 260

X 121 71 127 (continued)


96

Corrosion of Linings and Coatings TABLE 4.6 Continued Maximum Temperature Chemical Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid, 10% Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 15% Sodium hypochlorite, conc.

8F

8C

160 160 160

71 71 71

X X 212 212 212 212 80 160 230 140 140 X X 100 212 160 260 260 200 120 80 160 80 X X X X X 190 X 260 X 212

X X 100 100 100 100 27 71 110 60 60 X X 38 100 71 127 127 93 49 27 71 27 X X X X X 88 X 127 X 100

260 260

127 127

212 260 X X X X X

100 127 X X X X X (continued)



97

TABLE 4.6 Continued Maximum Temperature Chemical Sodium sulfide, to 10% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 100% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroaceteic acid, 30% White liquor Zinc chloride

8F

8C

260 260 250 160 X 80 80 X X X 160 X 212 80 140 160

127 127 121 71 X 27 27 X X X 71 X 100 27 60 71


4.10.6 Coal Tar Epoxy Coal tar epoxies can be applied to bare steel or concrete without a primer. They will not cure below 508F (108C) and have a temperature resistance of 2258F (1058C) dry or 1508F (668C) wet. They have a low cost per unit coverage. Coal tar epoxies combine the moisture resistance of coal tar with the chemical resistance of epoxy. It possesses excellent resistance to salt water, fresh water, mild acids, and mild alkalies, but has poor solvent resistance. Refer to Table 4.9 for the compatibility of coal tar epoxy with selected corrodents. Reference [1] has a more complete listing. Coal tar epoxy finds application as a coating for crude oil storage tanks, and in sewage disposal plants and water works. 4.10.7 Coal Tar Unless cross-linked with another resin, coal tar is thermoplastic and will flow at temperatures of 1008F (388C) or less. It hardens and embrittles in cold weather.


98

Corrosion of Linings and Coatings TABLE 4.7 Compatibility of Vinyl Ester with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium oxychloride Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride

8F

8C

X

X

200 180 150 150 100 X X 100 X 182 90 90 240 210 260 140 100 200 200 250 100 150 150 200 200 200 140 140 100 130 250

93 82 66 66 38 X X 38 X 82 32 32 116 99 127 60 38 93 93 121 38 66 66 93 93 93 60 60 38 54 121

180 200 220 120 220 110 210 120 X 160 X 260 200

82 93 104 49 104 38 99 49 X 71 X 127 93 (continued)



99

TABLE 4.7 Continued Maximum Temperature Chemical Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzenesulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine, liquid Butadiene n-Butylamine Butyl acetate Butyl alcohol Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chloroacetic acid Chloroacetic acid, 50% water Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10%

8F

8C

150 200 180 X X 200 180 100 90 210 200 100 100 X

66 93 82 X X 93 82 38 32 99 93 38 38 X

X 80 120 130

X 27 49 54

180 180 260 180 180 180 180 210 160 250 220 X 200 220 X 350 180 120 140 250 250 X 200 150 110 X X 150

82 82 127 82 82 82 82 99 71 116 104 X 93 104 X 177 82 49 60 121 121 X 93 66 43 X X 66 (continued)


100

Corrosion of Linings and Coatings TABLE 4.7 Continued Maximum Temperature Chemical Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dibutyl phthalate Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid, 10% Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 20% Nitric acid, 5%

8F

8C

X 210 210 210 210

X 99 99 99 99

220 210 240 X 260 220 150 150 200 100 110 210 210 210 200 200 200 X X 180 200 180 220 180 160 X X X 150 150 X 210 200 260 140 210

104 99 116 X 127 104 66 66 93 38 43 99 99 99 93 93 93 X X 82 93 82 104 82 71 X X X 66 66 X 99 93 127 60 99

X X 180 150 180

X X 82 66 82 (continued)



101

TABLE 4.7 Continued Maximum Temperature Chemical Nitric acid, 70% Nitrous acid, 10% Nitrous acid, anhydrous Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 100% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, fuming Sulfurous acid, 10% Thionyl chloride Toluene Trichloroacetic acid, 50% White liquor Zinc chloride

8F

8C

X 150 X X 150 X X 210 200 160 150

X 66 X X 66 X X 99 93 71 66

180 180 170 220

82 82 77 104

180 100 220 210 200 200 X 210 180 X X X 120 X 120 210 180 180

82 38 104 99 93 93 X 99 82 X X X 49 X 49 99 82 82


Coal tar exhibits excellent water resistance, good resistance to acids, alkalies, minerals, animal and vegetable oils, and salts. Table 4.10 provides the compatibility of coal tar with selected corrodents. Reference [1] provides a more extensive listing.


102

Corrosion of Linings and Coatings TABLE 4.8 Compatibility of Epoxy Polyamides with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, all conc. Acetic acid vapors Acetone Aluminum chloride, dry Aluminum fluoride Ammonium chloride, all Ammonium hydroxide, 25% Aqua regia, 3:1 Benzene Boric acid Bromine gas, dry Bromine gas, moist Calcium chloride Calcium hydroxide, all Citric acid, all conc. Diesel fuels Ethanol Ferric chloride Formaldehyde, to 50% Formic acid Glucose Green liquor Hydrobromic acid Hydrochloric acid, dil. Hydrochloric acid, 20% Hydrofluoric acid, dil. Hydrofluoric acid, 30% Hydrofluoric acid, vapors Hydrogen sulfide, dry Hydrogen sulfide, wet Iodine Lactic acid Lard oil Lauric acid Linseed oil Magnesium chloride, 50% Mercuric chloride Mercuric nitrate Methyl alcohol Methyl sulfate Methylene chloride Mineral oil Nitric acid Oil, vegetable Oleum Oxalic acid, all conc.

8F

8C

X X X X 100 X 100 100 X X 140 X X 110 140 100 100 100 100 100 X 100 100 X 100 X 100 X 100 100 100 X X X X 100 100 100 100 100 X X 100 X 100 X 100

X X X X 38 X 38 38 X X 60 X X 43 60 38 38 38 38 38 X 38 38 X 38 X 38 X 38 38 38 X X X X 38 38 38 38 38 X X 38 X 38 X 38 (continued)



103

TABLE 4.8 Continued Maximum Temperature Chemical Perchloric acid Petroleum oils, sour Phenol Phosphoric acid Potassium chloride, 30% Potassium hydroxide, 50% Propylene glycol Sodium chloride Sodium hydroxide, to 50% Sulfur dioxide, wet Sulfuric acid Water, demineralized Water, distilled Water, salt Water, sea Water, sewage White liquor Wines Xylene

8F

8C

X 100 X X 100 100 100 110 100 100 X 110 130 130 110 100 150 100 X

X 38 X X 38 38 38 43 38 38 X 43 54 54 43 38 66 38 X


Coal tar finds application as a coating both for interior and exterior of underground pipelines. 4.10.8 Urethanes Polyurethane-resin-based coatings are extremely versatile. They are priced higher than alkyds but lower than epoxies. Polyurethane resins are available as oil-modified, moisture-curing, bleached, two-component, and lacquers. Because of the versatility of the isocyanate reaction, wide diversity exists in specific coating properties. Exposure to the isocyanate should be minimized to avoid sensitivity that might result in an asthmatic-like breathing condition. Continued exposure to humidity may result in gassing or bubbling of the coating in humid conditions. The urethane coatings have a maximum operating temperature of 2508F (1218C) dry and 1508F (668C) wet. These coatings are resistant to most mineral and vegetable oils, greases, fuels, and to aliphatic and chlorinated hydrocarbons. Aromatic hydrocarbons, polar solvents, esters, ethers, and ketones will attack urethanes and alcohols will soften urethanes.


104

Corrosion of Linings and Coatings TABLE 4.9 Compatibility of Coal Tar Epoxy with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, to 20% Acetic acid, vapors Acetone Aluminum chloride, dry Aluminum fluoride Ammonium chloride, dry Ammonium hydroxide, 25% Aqua regia, 3:1 Benzene Boric acid Bromine gas, dry Bromine gas, moist Calcium chloride Calcium hydroxide, all Citric acid, all conc. Diesel fuels Ethanol Ferric chloride Formaldehyde, to 50% Formic acid Glucose Green liquor Hydrobromic acid Hydrochloric acid, dil. Hydrochloric acid, 20% Hydrofluoric acid, dil. Hydrofluoric acid, 30% Hydrofluoric acid, vapors Hydrogen sulfide, dry Hydrogen sulfide, wet Iodine Lactic acid Lard oil Lauric acid Linseed oil Magnesium chloride, 50% Mercuric chloride Mercuric nitrate Methyl alcohol Methyl sulfate Methylene chloride Mineral oil Nitric acid Oil vegetable Oleum Oxalic acid, all conc.

8F

8C

X 100 100 X 100 120 100 110 X X 100 100 X 100 100 100 100 100 100 100 X 100 100 X 100 X 100 X 110 100 100 X X X X 100 90 100 100 100 X X 100 X 100 X 100

X 38 38 X 38 49 88 43 X X 38 38 X 38 38 38 38 38 38 38 X 38 38 X 38 X 38 X 43 38 38 X X X X 38 32 38 38 38 X X 38 X 38 X 38 (continued)



105

TABLE 4.9 Continued Maximum Temperature Chemical Perchloric acid Petroleum oils, sour Phenol Phosphoric acid Potassium chloride, 30% Potassium hydroxide, 50% Propylene glycol Sodium chloride Sodium hydroxide, to 50% Sulfur dioxide, wet Sulfuric acid Water, demineralized Water, distilled Water, salt Water, sea Water, sewage White liquor Wines Xylene

8F

8C

X 100 X X 100 100 100 110 100 100 X 100 100 130 90 100 100 100 X

X 38 X X 38 38 38 43 38 38 X 38 38 54 32 38 38 38 X


Urethane finds limited service in weak acid solutions and cannot be used in concentrated acids. Urethanes are not resistant to steam or caustics, but they are resistant to deteriorating effects of being immersed in water. Refer to Table 4.11 for the compatibility of urethane with selected corrodents and Reference [1] for a more comprehensive listing. It is possible to apply uniform coatings or films of urethane to a variety of substrate materials including glass, metal, wood, fabric, and paper. Urethane coatings are often applied to the interior of pipes and tanks. Filtration units, clarifiers, holding tanks, and treatment sumps constructed of reinforced concrete are widely used in the treatment of municipal, industrial, and thermal generating station wastewater. In many cases, particularly in anaerobic, industrial and thermal generating systems, urethane linings are used to protect the concrete from severe chemical attack and prevent seepage into the concrete of chemicals that can attack the reinforcing steel. These linings provide protection against abrasion and erosion, and act as a waterproofing system to combat leakage of the equipment resulting from concrete movement and shrinkage.


106

Corrosion of Linings and Coatings TABLE 4.10 Compatibility of Coal Tar with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, all conc. Acetic acid, vapors Acetone Aluminum chloride, dry Aluminum fluoride Ammonium chloride, all Ammonium hydroxide, 25% Aqua regia, 3:1 Benzene Boric acid Bromine gas, dry Bromine gas, moist Calcium chloride Calcium hydroxide, all conc. Citric acid, all conc. Diesel fuels Ethanol Ferric chloride Formaldehyde, to 50% Formic acid Glucose Green liquor Hydrobromic acid Hydrochloric acid, dil. Hydrochloric acid, 20% Hydrofluoric acid, dil. Hydrofluoric acid, 30% Hydrofluoric acid, vapors Hydrogen sulfide, dry Hydrogen sulfide, wet Iodine Lactic acid Lard oil Lauric acid Linseed oil Magnesium chloride, 50% Mercuric chloride Mercuric nitrate Methyl alcohol Methyl sulfate Methylene chloride Mineral oil Nitric acid Oil vegetable Oleum

8F

8C

X

X

X

X

X X

X X

X X

X X

X X

X X

X X X X X X

X X X X X X

X X X X

X X X X

X

X

X

X

X

X (continued)



107

TABLE 4.10 Continued Maximum Temperature Chemical Oxalic acid, all conc. Perchloric acid Petroleum oils, sour Phenol Phosphoric acid Potassium chloride, 30% Potassium hydroxide, 50% Propylene glycol Sodium chloride Sodium hydroxide, to 50% Sulfur dioxide, wet Sulfuric acid Water, demineralized Water, distilled Water, salt Water, sea Water, sewage White liquor Wines Xylene

8F

8C

X

X

X X

X X

X 90

X 32

90 90

32 32

X

X


4.10.9 Neoprene Neoprene is one of the oldest and most versatile of the synthetic rubbers. Chemically, it is polychloroprene. Its basic unit is a chlorinated butadiene whose formula is: Cl CH2

C

CH

CH2

The raw material is acetylene, which makes this product more expensive than some of the other elastomeric materials. As with other lining materials, neoprene is available in a variety of formulations. Depending on the compounding procedure, material can be produced to impart specific properties to meet application needs.


108

Corrosion of Linings and Coatings TABLE 4.11 Compatibility of Urethanes with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, all conc. Acetic acid, vapors Acetone Aluminum chloride, dry Aluminum fluoride Ammonium chloride, all Ammonium hydroxide, 25% Aqua regia, 3:1 Benzene Boric acid Bromine gas, dry Bromine gas, moist Calcium chloride Calcium hydroxide, all Citric acid, all conc. Diesel fuels Ethanol Ferric chloride Formaldehyde, to 50% Formic acid Glucose Green liquor Hydrobromic acid Hydrochloric acid, dil. Hydrochloric acid, 20% Hydrofluoric acid, dil. Hydrofluoric acid, 30% Hydrofluoric acid vapors Hydrogen sulfide, dry Hydrogen sulfide, wet Iodine Lactic acid Lard oil Lauric acid Linseed oil Magnesium chloride, 50% Mercuric chloride Mercuric nitrate Methyl alcohol Methyl sulfate Methylene chloride Mineral oil Nitric acid Oil vegetable

8F

8C

X 90 90 90

X 32 32 32

90 90 X X 90

32 32 X X 32

80 90

27 32

90 90

32 32

X X

X X

X X

X X

90

32

90 90

32 32

90

32

X 90 X

X 32 X (continued)



109

TABLE 4.11 Continued Maximum Temperature Chemical Oleum Oxalic acid, all conc. Perchloric acid Petroleum oils, sour Phenol Phosphoric acid Potassium chloride, 30% Potassium hydroxide, 50% Propylene glycol Sodium chloride Sodium hydroxide, to 50% Sulfur dioxide, wet Sulfuric acid, 10% Water, demineralized Water, distilled Water, salt Water, sea Water, sewage White liquor Wines Xylene

8F

8C

X

X

X

X

X

X

90 90

32 32

80 90

27 32

90

32

90 X 80

32 X 27

X X

X X


Neoprene is also available in a variety of forms. In addition to a neoprene latex that is similar to natural rubber latex, neoprene is produced in fluid form as either a compounded latex dispersion or solvent solution. After these materials have solidified or cured, they have the same physical and mechanical properties as the solid or cellular forms of neoprene. Neoprene solvent solutions are prepared by dissolving neoprene in standard rubber solvents. These solutions can be formulated in a range of viscosities suitable for application by brush, spray, or roller. Major areas of application include linings for storage tanks, industrial equipment, and chemical processing equipment. These coatings protect the vessels from corrosion by acids, salts, oils, alkalies, and most hydrocarbons. Neoprene possesses excellent resistance to attack from solvents, waxes, fats, oils, greases, and many other petroleum-based products. It also exhibits excellent service in contact with aliphatic compounds (methyl and ethyl


110


alcohols, ethylene glycols, etc.) and aliphatic hydrocarbons. It is also resistant to dilute mineral acids, inorganic salt solutions, and alkalies. Chlorinated and aromatic hydrocarbons, organic esters, aromatic hydroxy compounds, and certain ketones will attack neoprene. Refer to Table 4.12 for the compatibility of neoprene with selected corrodents and Reference [1] for a more complete listing. 4.10.10 Polysulfide Rubber Polysulfide rubbers are manufactured by combining ethylene (CH2aCH2) with an alkaline polysulfide. Morton Thiokol, Inc. markets a series of liquid polysulfides that can be oxidized to rubbers. The polysulfide rubbers possess outstanding resistance to solvents. They exhibit excellent resistance to oils, gasoline and aliphatic and aromatic hydrocarbon solvents, very good resistance to water, good alkali resistance, and fair acid resistance. Contact with strong concentrated inorganic acids such as sulfuric, nitric, or hydrochloric, should be avoided. Refer to Table 4.13 for the compatibility of polysulfides with selected corrodents and Reference [1] for a more comprehensive listing. 4.10.11 Hypalon Chlorosulfonated polyethylene synthetic rubber is manufactured by DuPont under the trade name Hypalon. In many respects, it is similar to neoprene but it does possess some advantages over neoprene in certain types of service. It has better heat and ozone resistance and better chemical resistance. Hypalon has a broad range of service temperatures with excellent thermal properties. General purpose compounds can operate continuously at temperatures of 248–2758F (120–1358C). Special compounds can be formulated that can be used intermittently up to 3028F (1508C). On the low temperature side, conventional compounds can be used continuously down to 0 to K208 F (K18 to K288C). When properly compounded, Hypalon is resistant to attack by hydrocarbon oils and fuels, even at elevated temperatures. It is also resistant to such oxidizing chemicals as sodium hypochlorite, sodium peroxide, ferric chlorides, and sulfuric, chromic and hydrofluoric acids. Concentrated hydrochloric acid (37%) at elevated temperatures (above 1588F (708C)) will attack hypalon, but can be handled with no adverse effects at all concentrations below that temperature. Nitric acid up to 60% concentration at room temperature can also be handled without adverse effect. Hypalon is also resistant to salt solutions, alcohols, and both weak and concentrated alkalies. Long-term contact with water has little effect on Hypalon. Hypalon has poor resistance to aliphatic, aromatic, and chlorinated hydrocarbons, aldehydes, and ketones. Refer to Table 4.14 for the



111

TABLE 4.12 Compatibility of Neoprene with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aq. Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium oxychloride Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate

8F

8C

200 200 160 160 160 X X X X X 140 160 120 X 200

93 93 71 71 71 X X X X X 60 71 49 X 93

150

66

200 180 200 200 140 X 200 150 150 150 200 200 200 200 200

93 82 93 93 60 X 93 66 66 66 93 93 93 93 93

200 150 150 160

93 66 66 71

X 200 X X 140 X 150

X 93 X X 60 X 66 (continued)


112

Corrosion of Linings and Coatings TABLE 4.12 Continued Maximum Temperature Chemical Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine, liquid Butadiene Butyl acetate Butyl alcohol Butyl phthalate n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chloroacetic acid Chloroacetic acid, 50% water Chlorobenzene

8F

8C

150 230 200 200 X X 100 150 X X 200 150 X X X 140 60 200

66 110 93 93 X X 38 66 X X 93 66 X X X 60 16 93

X

X

X 200 200 150 230 230 X 150 200 150

X 93 93 66 110 110 X 66 93 66

X 200 200 X X X 150 X X X X X X X

X 93 93 X X X 66 X X X X X X X (continued)



113

TABLE 4.12 Continued Maximum Temperature Chemical Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone

8F

8C

X X 140 100

X X 60 38

150 150 160

66 66 71

200 160 200 X 200 160 X X X X 100 160 160 200 90 200 X X X X X X X X X X X X 80 X 140 90 200


200 X X X

93 X X X (continued)


114

Corrosion of Linings and Coatings TABLE 4.12 Continued Maximum Temperature Chemical Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

8F

8C

X X X X X X X

X X X X X X X

X X 150 200 160

X X 66 93 71

200 200 230 230 230 X X 200 200 X 150 100 X X X X X 100 X X X 140 160

93 93 110 110 110 X X 93 93 X 66 38 X X X X X 38 X X X 60 71




115

TABLE 4.13 Compatibility of Polysulfides with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, all conc. Acetic acid vapors Acetone Aluminum chloride, dry Aluminum fluoride Ammonium chloride, all Ammonium hydroxide, 25% Aqua regia, 3:1 Benzene Boric acid Bromine gas, dry Bromine gas, moist Calcium chloride Calcium hydroxide, all Citric acid, all conc. Diesel fuels Ethanol Ferric chloride Formaldehyde, to 50% Formic acid Glucose Green liquor Hydrobromic acid Hydrochloric acid, dil. Hydrochloric acid, 20% Hydrofluoric acid, dil. Hydrofluoric acid, 30% Hydrofluoric acid, vapors Hydrogen sulfide, dry Hydrogen sulfide, wet Iodine Lactic acid Lard oil Lauric acid Linseed oil Magnesium chloride, 50% Mercuric chloride Mercuric nitrate Methyl alcohol Methyl sulfate Methylene chloride Mineral oil Nitric acid Oil vegetable Oleum

8F

8C

80 90 80

27 32 27

140 X

66 X

X

X

150 X X 80 150

66 X X 27 66

80

27

X X X X

X X X X

X

X

150

66

80

27

80 X X X

27 X X X (continued)


116

Corrosion of Linings and Coatings TABLE 4.13 Continued Maximum Temperature Chemical Oxalic acid, all conc. Perchloric acid Petroleum oils, sour Phenol Phosphoric acid Potassium chloride, 30% Potassium hydroxide, 50% Propylene glycol Sodium chloride Sodium hydroxide, to 50% Sulfur dioxide, wet Sulfuric acid Water, demineralized Water, distilled Water salt Water, sea Water, sewage White liquor Wines Xylene

8F

8C

X

X

X X

X X

80

27

80 X

27 X

X 80 80 80 80 80

X 27 27 27 27 27

X 80

X 27


compatibility of Hypalon with selected corrodents and Reference [1] for a more complete listing. Hypalon finds useful applications in many industries and many fields. Because of its outstanding resistance to oxidizing acids, it is used to line railroad tank cars and other tanks containing oxidizing chemicals and acids. 4.10.12 Plastisols PVC plastisols are dispersions of PVC and/or PVC copolymer resins in compatible plasticizers. These liquids can vary in viscosity from thin, milklike fluids to heavy pastes having the consistency of molasses. The lowest viscosity products are generally used for spray coating. PVC plastisol coatings have limited adhesion and require primers; the coatings must be heat cured.



117

TABLE 4.14 Compatibility of Hypalon with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonia carbonate Ammonia gas Ammonium chloride, 10% Ammonium chloride, 10% Ammonium chloride, 50% Ammonium fluoride, sat. Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax

8F

8C

60 X 200 200 200 X 200 X X 140 140 200 200 200 200 180 140 90 190 200 190 190 200 200 200 80 140 200 200 60 200 X 140 140 200 200 200 200 200 X X X 200 140 X 200

16 X 93 93 93 X 93 X X 60 60 93 93 93 93 82 60 32 88 93 88 88 93 93 93 27 60 93 93 16 93 X 60 60 93 93 93 93 93 X X X 93 60 X 93 (continued)


118

Corrosion of Linings and Coatings TABLE 4.14 Continued Maximum Temperature Chemical Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyric acid Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Chloracetic acid Chlorine gas, dry Chlorine gas, wet Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroethane (ethylene dichloride)

8F

8C

200 60 60 60 X 60 200 X 200 90 90 200 200 200 200 100 200 200 X 200 200 200 X 200 X X X 90 X X X 150 150

93 16 16 16 X 16 93 X 93 32 32 93 93 93 93 38 93 93 X 93 93 93 X 93 X X X 32 X X X 66 66

200 200 X 200 200 200 X 200 200 X X X

93 93 X 93 93 93 X 93 93 X X X (continued)



119

TABLE 4.14 Continued Maximum Temperature Chemical Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Fluorine gas, dry Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride

8F

8C

200 200 200 200 200 140 100 100 90 160 140 90 90 90 90 X X 140 80 200 180 X X X 140 100 100 X X X 100 90 X 200 80 200 200 200 200 200 200 200

93 93 93 93 93 60 38 38 32 71 60 32 32 32 32 X X 60 27 93 82 X X X 60 38 38 X X X 38 32 X 93 27 93 93 93 93 93 93 93

200 90 200

93 32 93 (continued)


120

Corrosion of Linings and Coatings TABLE 4.14 Continued Maximum Temperature Chemical Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfurous acid Toluene Zinc chloride

8F

8C

200 200 160 X X X 160 X 200

93 93 71 X X X 71 X 93

The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. Source: From P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.

The viscosity of plastisol is controlled by formulator techniques, and is often kept low by the addition of inactive diluents such as odorless mineral spirits. If more than minor amounts of diluents are used, the product is often referred to as an organsol. These compounds share common compounding technology. The primary components are the dispersion grade resin, plasticizers, PVC stabilizers (which are common to all PVC), and assorted fillers, pigments, and a wide variety of additives to control properties of the product in storage, during processing, and in the finished state. Plasticizers are liquids that provide mobility to the plastisol system. They are of primary significance, and they are selected first when formulating. Plasticizers differ in the performance characteristics that they impart to the finished product. The blend of plasticizers will also assist in the control of viscosity and its stability, and in the fusion characteristics of the finished plastisol. Because plasticized PVC is compounded of a PVC dispersion of high molecular weight vinyl chloride polymers in a suitable liquid plasticizer, formulations can be made for special applications. By selective compounding, both physical and corrosion-resistant properties can be modified. For certain applications, this feature can be advantageous. Two types of PVC resin are produced: normal impact (type 1) and high impact (type 2). Type 1 is unplasticized PVC having normal impact and optimum chemical resistance. Type 2 is a plasticized PVC and has optimum impact strength and reduced chemical resistance. Plastisol PVC is the latter type.



121

Type 1 PVC resists attack by most acids and strong alkalies, gasoline, kerosene, aliphatic alcohols, and hydrocarbons. It is particularly useful in the handling of hydrochloric acid. The chemical resistance of type 2 PVC (plastisol) to oxidizing and highly alkaline chemicals is reduced. Plastisol can be attacked by aromatics, chlorinated organic compounds, and lacquer solvents. In addition to handling highly corrosive and abrasive chemicals, many applications have also been found in marine environments. Table 4.15 lists the compatibility of plastisols with selected corrodents and Reference [1] provides additional listings. Vinyl plastisols are popular for use as an acid-resisting coating. Plastisol has a maximum operating temperature of 1408F (608C). 4.10.13 Perfluoroalkoxy Perfluoroalkoxy (PFA) is manufactured by DuPont. It is not degraded by systems commonly encountered in chemical processes. It is inert to strong mineral acids, inorganic bases, inorganic oxidizing agents, salt solutions, and such organic compounds as organic acids, aldehydes, anhydrides, aliphatic hydrocarbons, alcohols, esters, ethers, chlorocarbons, fluorocarbons, and mixtures of the above. Refer to Table 4.16 for the compatibility of PFA with selected corrodents and Reference [1] for additional listings. PFA will be attacked by certain halogen complexes containing fluorine. These include chlorine trifluoride, bromine trifluoride, iodine pentafluoride, and fluorine itself. It is also attacked by such metals as sodium or potassium, particularly in their molten states. Standard lining thickness is nominally 0.040 in. on interior and wetted surfaces. When abrasion is a problem, a thickness of 0.090 in. is available. Coatings applied on carbon steel or stainless steel have a continuous service temperature of between K608F (K518C) and 4008F (2048C). A primer is required prior to applying the coating. If damaged, the coating cannot be repaired. Heat is required to cure the coating. Applications are used to provide corrosion protection, nonstick surfaces, and purity protection of chemicals being handled. 4.10.14 Fluorinated Ethylene Propylene Fluorinated Ethylene Propylene (FEP) is a fluorinated thermoplast but is less expensive than PTFE (Teflon). With few exceptions, FEP exhibits the same corrosion resistance as PTFE but at a lower temperature. It is resistant to practically all chemicals, the exception being extremely potent oxidizers such as chlorine trifluoride, and related compounds. Some chemicals in high concentrations will attack FEP when at or near the service temperature limit. Refer to Table 4.17 for the compatibility of FEP with selected corrodents and Reference [1] for additional listings.


122

Corrosion of Linings and Coatings TABLE 4.15 Compatibility of Plastisols with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aq. Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide

8F

8C

X X 100 90 X X X X X X X 140 90 X 140 100 140 140 140 140 140 140 140 90 140 140 140 140 90 90 140 140 140 140 140 140 140 X X X X 140 X 140 140 140

X X 38 32 X X X X X X X 60 32 X 60 38 60 60 60 60 60 60 60 32 60 60 60 60 32 32 60 60 60 60 60 60 60 X X X X 60 X 60 60 60 (continued)



123

TABLE 4.15 Continued Maximum Temperature Chemical Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15% Citric acid, conc.

8F

8C

140 140 X X 140 140 X 140 140 X X X 60 X X X X 140 X 140 140 140 140 140 140 140 140 140 140 140 140 X 140 X 140 X 105 140 X X X X 60 140 X 140 140

60 60 X X 60 60 X 60 60 X X X 16 X X X X 60 X 60 60 60 60 60 60 60 60 60 60 60 60 X 60 X 60 X 40 60 X X X X 16 60 X 60 60 (continued)


124

Corrosion of Linings and Coatings TABLE 4.15 Continued Maximum Temperature Chemical Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hypochlorous acid Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid

8F

8C

140 140 140 140 X X 120 X

60 60 60 60 X X 49 X

140 140 140 140 140 X X 140 140 140 140 140 140 120 68 140 X 140 80 140 140 X X X 140 100 140 70 X 60 X 60 60 X 140 X 140 X

60 60 60 60 60 X X 60 60 60 60 60 60 49 20 60 X 60 27 60 60 X X X 60 38 60 23 X 16 X 16 16 X 60 X 60 X (continued)



125

TABLE 4.15 Continued Maximum Temperature Chemical Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

8F

8C

105 140 140 140 140 140 140 140 140 140 140 140 140 140 X X X X 140 X X X 140 140

40 60 60 60 60 60 60 60 60 60 60 60 60 60 X X X X 60 X X X 60 60


Coating thickness range from 0.010 to 0.060 in. with a maximum service temperature of 3908F (1998C). Damage to these coatings cannot be repaired. The coating is a fusion from a water or solvent dispersion and requires a heat cure temperature of 500–6608F (260–3158C). Application is by spray. Previously glass-linked tanks can be refurbished with this lining. 4.10.15 PTFE (Teflon) PTFE coatings are spray applied as water or solvent dispersions. They require heat curing at approximately 7508F (3998C). Their maximum service temperature is 5008F (2608C). PTFE is chemically inert in the presence of most corrodents. There are very few chemicals that will attack PTFE within normal use temperatures.


126

Corrosion of Linings and Coatings TABLE 4.16 Compatibility of PFA with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aq. Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gasa Ammonium bifluoridea Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10%a Ammonium fluoride, 25%a Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Anilineb Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 (continued)



127

TABLE 4.16 Continued Maximum Temperature Chemical b

Benzaldehyde Benzene sulfonic acid, 10% Benzenea Benzoic acid Benzyl alcoholb Benzyl chloridea Borax Boric acid Bromine gas, drya Bromine, liquida,b Butadienea Butyl acetate Butyl alcohol Butyl phthalate n-Butylamineb Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfidea Carbon dioxide, dry Carbon dioxide, wet Carbon disulfidea Carbon monoxide Carbon tetrachloridea,b,c Carbonic acid Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, weta Chlorine, liquidb Chlorobenzenea Chloroforma Chlorosulfonic acidb Chromic acid, 10% Chromic acid, 50%b Chromyl chloride

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 X 450 X 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 X 232 X 232 232 232 232 232 232 (continued)


128

Corrosion of Linings and Coatings TABLE 4.16 Continued Maximum Temperature Chemical Citric acid, 15% Citric acid, conc. Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride)a Ethylene glycol Ferric chloride Ferric chloride, 50% in waterb Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20%a,c Hydrobromic acid, 50%a,c Hydrobromic acid, dil.a,c Hydrochloric acid, 20%a,c Hydrochloric acid, 38%a,c Hydrocyanic acid, 10% Hydrofluoric acid, 30%a Hydrofluoric acid, 70%a Hydrofluoric acid, 100%a Hypochlorous acid Iodine solution, 10%a Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloridea Methyl ethyl ketonea Methyl isobutyl ketonea Muriatic acida Nitric acid, 5%a Nitric acid, 20a Nitric acid, 70%a Nitric acid, anhydrousa Nitrous acid, 10%

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232

450 450 450 450 450 450 X X 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 X X 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 (continued)



129

TABLE 4.16 Continued Maximum Temperature Chemical Oleum Perchloric acid, 10% Perchloric acid, 70% Phenola Phosphoric acid, 50–80%b Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuminga Sulfurous acid Thionyl chloridea Toluenea Trichloroacetic acid White liquor Zinc chlorideb

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232

The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. A blank space indicates that the data is unavailable. a b c

Material will permeate. Material will be absorbed. Material will cause stress cracking.

Source: From P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.

These reactants are among the most violent oxidizing and reducing agents known. Elemental sodium in contact with fluorocarbons removes fluorine from the polymer molecule. The other alkali metals (potassium, lithium, etc.) react in a similar manner.


130

Corrosion of Linings and Coatings TABLE 4.17 Compatibility of FEP with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetonea Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aq. Aluminum chloride, dry Aluminum fluorideb Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gasb Ammonium bifluorideb Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10%b Aluminum fluoride, 25%b Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Anilinea Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride

8F

8C

200 400 400 400 400 400 400 400 400 200 400 400 400 400 400 400 400 300 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 250 400 400 400

93 204 204 204 204 204 204 204 204 93 204 204 204 204 204 204 204 149 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 121 204 204 204 (continued)



131

TABLE 4.17 Continued Maximum Temperature Chemical Barium hydroxide Barium sulfate Barium sulfide Benzaldehydea Benzenea,b Benzenesulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dryb Bromine gas, moistb Bromine liquida,b Butadieneb Butyl acetate Butyl alcohol n-Butylaminea Butyl phthalate Butyric acid Calcium bisulfide Calcium bisulfideb Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloridea,b,c Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wetb Chlorine, liquida Chlorobenzeneb Chloroformb Chlorosulfonic acida

8F

8C

400 400 400 400 400 400 400 400 400 400 400 200 200 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 X 400 400 400 400 400

204 204 204 204 204 204 204 204 204 204 204 93 93 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 X 204 204 204 204 204 (continued)


132

Corrosion of Linings and Coatings TABLE 4.17 Continued Maximum Temperature Chemical Chromic acid, 10% Chromic acid, 50%a Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride)b Ethylene glycol Ferric chloride Ferric chloride, 50% in watera Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20%b,c Hydrobromic acid. 50%b,c Hydrobromic acid, dil. Hydrochloric acid, 20%b,c Hydrochloric acid, 38%b,c Hydrocyanic acid, 10%b Hydrofluoric acid, 30%b Hydrofluoric acid, 70%b Hydrofluoric acid, 100%b Hypochlorous acid Iodine solution, 10%b Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chlorideb Methyl ethyl ketoneb Methyl isobutyl ketoneb Muriatic acidb Nitric acid, 5%b

8F

8C

400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400

204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204

400 400 260 260 400 400 200 X 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 300 400 400 400 400 400

204 204 127 127 204 204 93 X 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 149 204 204 204 204 204 (continued)



133


Nitric acid, 20% Nitric acid. 70%b Nitric acid, anhydrousb Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenolb Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10%a Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fumingb Sulfurous acid Thionyl chlorideb Tolueneb Trichloroacetic acid White liquor Zinc chloridec

8F

8C

400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400

204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204


Material will be absorbed. Material will permeate. Material will cause stress cracking.



134


Fluorine and related compounds (e.g., chlorine trifluoride) are absorbed into the PTFE resin with such intimate contact that the mixture becomes sensitive to a source of ignition, such as impact. The handling of 80% sodium hydroxide, aluminum chloride, ammonia, and certain amines at high temperature may produce the same effect as elemental sodium. Also, slow oxidative attack can be produced by 70% nitric acid under pressure at 4888F (2508C). Refer to Table 4.18 for the compatibility of PTFE with selected corrodents and Reference [1] for additional listings. 4.10.16 Tefzel Tefzel (ETFE) is a trademark of DuPont. ETFE is a modified, partially fluorinated copolymer of ethylene and polytetrafluoroethylene (PTFE). Because it contains more than 75% by weight PTFE it has better resistance to abrasion and cut-through than PTFE, while retaining most of the corrosionresistant properties. The typical Tefzel coating thickness is nominally 0.040 in. thick on all interior surfaces and flange faces. Coating thickness from 0.020 to 0.090 in. are available, depending on application requirements and part geometry. For coatings or linings applied on carbon steel or stainless steel, the continuous service temperature range is from K258F (K328C) to 2258F (1078C). Tefzel is inert to strong mineral acids, inorganic bases, halogens, and strong metal salt solutions. Even carboxylic acids, aromatic and aliphatic hydrocarbons, alcohols, ketones, aldehydes, ethers, chlorocarbons, and classic polymer solvents have little effect on Tefzel. Very strong oxidizing acids near their boiling points, such as nitric acid at high concentrations, will effect ETFE to varying degrees as will strong organic bases such as amines and sulfonic acids. Refer to Table 4.19 for the compatibility of ETFE with selected corrodents and Reference [1] for additional listings. 4.10.17 Halar Halar (ECTFE) is manufactured under the trade name of Halar by Ausimont. Ethylene–chlorotrifluoroethylene is a 1:1 alternating copolymer of ethylene and chlorotrifluoroethylene. This chemical structure gives the polymer a unique combination of properties. It possesses excellent chemical resistance and, of all the fluoropolymers, ECTFE ranks among the best for abrasion resistance. The resistance to permeation by oxygen, carbon dioxide, chlorine gas, or hydrochloric acid is superior to that of PTFE or FEP, being 10–100 times better. Water absorption is less than 0.1%. Halar exhibits outstanding chemical resistance. It is virtually unaffected by all corrosive chemicals commonly encountered in industry, including strong mineral and oxidizing acids, alkalies, metal etchants, liquid oxygen, and essentially all organic solvents except hot amines (e.g., aniline



135

TABLE 4.18 Compatibility of PTFE with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aq. Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gasa Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 (continued)


136

Corrosion of Linings and Coatings TABLE 4.18 Continued Maximum Temperature Chemical Benzaldehyde Benzene sulfonic acid, 10% Benzenea Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, drya Bromine liquida Butadienea Butyl acetate Butyl alcohol n-Butylamine Butyl phthalate Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon disulfidea Carbon monoxide Carbon tetrachlorideb Carbonic acid Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, weta Chlorine, liquid Chlorobenzenea Chloroforma Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15%

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 X 450 X 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 X 232 X 232 232 232 232 232 232 232 (continued)



137

TABLE 4.18 Continued Maximum Temperature Chemical Citric acid, conc. Copper carbonate Copper chloride Copper cyanide, 10% Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroethane (ethylene dichloride)a Dichloroethane acid Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20%b Hydrobromic acid, 50%b Hydrobromic acid, dil.a,b Hydrochloric acid, 20%b Hydrochloric acid, 38%b Hydrocyanic acid, 10%b Hydrofluoric acid, 30%b Hydrofluoric acid, 70%b Hydrofluoric acid, 100%a Hypochlorous acid Iodine solution, 10%a Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloridea Methyl ethyl ketonea Methyl isobutyl ketoneb Muriatic acida Nitric acid, 20%a Nitric acid, 5%a Nitric acid, 70%a Nitric acid, anhydrousa Nitrous acid, 10% Oleum

8F

8C

450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232

450 450 450 450 450 450 450 X X 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 X X 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 (continued)


138

Corrosion of Linings and Coatings TABLE 4.18 Continued Maximum Temperature Chemical Perchloric acid, 10% Perchloric acid, 70% Phenola Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfurous acid Sulfurous acid, fuminga Thionyl chloride Toluenea Trichloroacetic acid White liquor Zinc chloridec

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232


Material will permeate. Material will cause stress cracking. Material will be absorbed.


dimethylamine). As with other fluorocarbons, Halar will be attacked by metallic sodium and potassium. Refer to Table 4.20 for the compatibility of ECTFE with selected corrodents and Reference [1] for additional listings. Coating thickness range from 0.010 to 0.040 in. with a temperature range from cryogenic to 3208F (1608C). In addition to its corrosion resistance,



139

TABLE 4.19 Compatibility of ETFE with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aq. Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide

8F

8C

200 250 250 250 230 230 300 150 150 150 280 210 190 300 300 300 300 300 300 300 300 300 300 300 290 300 300 300 300 300 230 300 300 300 300 250 300 300 230 210 210 300 300 300 300 300

93 121 121 121 110 110 149 66 66 66 138 99 88 149 149 149 149 149 149 149 149 149 149 149 143 149 149 149 149 149 110 149 149 149 140 121 149 149 110 99 99 149 149 149 149 149 (continued)


140

Corrosion of Linings and Coatings TABLE 4.19 Continued Maximum Temperature Chemical Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine water, 10% Butadiene Butyl acetate Butyl alcohol Butyl phthalate n-Butylamine Butyric acid Calcium bisulfide Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid, 50% Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet Chlorine, water Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15%

8F

8C

210 210 210 270 300 300 300 300 150 230 250 230 300 150 120 250 300 300 300 300 300 300 300 300 260 300 210 150 300 300 150 300 270 300 300 230 230 210 250 100 210 230 80 150 150 210 120

99 99 99 132 149 149 149 149 66 110 121 110 149 66 49 121 149 149 149 149 149 149 149 149 127 149 99 66 149 149 66 149 132 149 149 110 110 99 121 38 99 110 27 66 66 99 49 (continued)



141

TABLE 4.19 Continued Maximum Temperature Chemical Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cyclohexane Cyclohexanol Dichloroacetic acid Ethylene glycol Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid

8F

8C

300 300 300 270 300 300 250 150 300 300 300 300 300 100 100 300 300 300 300 300 300 270 250 230 300 250 250 300 270 120 300 230 300 300 150 150 80 X 210 150 230 150 210 270 130 300 250

149 149 149 132 149 149 121 66 149 149 149 149 149 38 38 149 149 149 149 149 149 132 121 110 149 121 121 149 132 49 149 110 149 149 66 66 27 X 99 66 110 66 99 132 54 149 121 (continued)


142

Corrosion of Linings and Coatings TABLE 4.19 Continued Maximum Temperature Chemical Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid. 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid Zinc chloride

8F

8C

300 300 230 230 300 300 300 300 300 300 300 300 300 300 300 120 210 210 250 210 300

149 149 110 110 149 149 149 149 149 149 149 149 149 149 149 49 99 99 121 99 149


the material has excellent impact strength and abrasion resistance. Previously glass-lined vessels can be refurbished using ECTFE. 4.10.18 Fluoroelastomers Fluoroelastomers (FKM) are fluorine-containing hydrocarbon polymers with a saturated structure obtained by polymerizing fluorinated monomers such as vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene. They are manufactured under trade names such as Viton by DuPont, Technoflon by Ausimont, and Fluorel by 3M. The FKM have been approved by the U.S. Food and Drug Administration for use in repeated contact with food products. More details are available in the Federal Register (Vol. 33, No. 5, January 9, 1968), Part 121—Food Additives, Subpart F—Food Additives Resulting from Contact with Containers or Equipment and Food Additives Otherwise Affecting Food-Rubber Articles Intended for Repeated Use.



143

TABLE 4.20 Compatibility of ECTFE with Selected Corrodents Maximum Temperature Chemical Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl chloride Alum Aluminum chloride, aq. Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10%a Ammonium fluoride. 25%a Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Anilineb Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde

8F

8C

250 250 150 200 100 150 150 150 150 300 300 300

121 121 66 93 38 66 66 66 66 149 149 149

300 300 300 150 300 300 300 300 290 300 300 300 300 300 300 300 150 300 300 300 160 300 300 90 100 250 300 300 300 300 300 150

149 149 149 66 149 149 149 149 143 149 149 149 149 149 149 149 66 149 149 149 71 149 149 32 38 121 149 149 149 149 149 66 (continued)


144

Corrosion of Linings and Coatings TABLE 4.20 Continued Maximum Temperature Chemical Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50%b Citric acid, 15% Citric acid, conc. Copper carbonate

8F

8C

150 150 250 300 300 300 300 X 150 250 150 300 250 300 300 300 300 300 300 300 300 300 300 300 220 80 300 300 80 150 300 300 300 250 250 150 250 250 150 250 80 250 250 300 300 150

66 66 121 149 149 149 149 X 66 121 66 149 121 149 149 149 149 149 149 149 149 149 149 149 104 27 149 149 27 66 149 149 149 121 121 66 121 121 66 121 27 121 121 149 149 66 (continued)



145

TABLE 4.20 Continued Maximum Temperature Chemical Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20%a Nitric acid, 70%a Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid

8F

8C

300 300 300 300 300 300 300 300 300 300 300 300 300 300 X 80 300 300 300 300 300 300 250 240 240 300 250 150 150 300 250 300 150 150 300 300 250 150 150 250 X 150 150 150 250 88

149 149 149 149 149 149 149 149 149 149 149 149 149 149 X 27 149 149 149 149 149 149 121 116 116 149 121 66 66 149 121 149 66 66 149 149 121 66 66 121 X 66 66 66 121 27 (continued)


146

Corrosion of Linings and Coatings TABLE 4.20 Continued Maximum Temperature Chemical Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

8F

8C

300 250 300 300 300 250 150 300 300 300 300 300 250 250 250 150 150 80 300 250 150 150 150 250 300

149 121 149 149 149 121 66 149 149 149 149 149 121 121 121 66 66 27 149 121 66 66 66 121 149

The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. A blank space indicates that the data is unavailable. a b

Material will permeate. Material will be absorbed.


As with other rubbers, fluoroelastomers are capable of being compounded with various additives to enhance specific properties for particular applications. FKM coatings have an allowable temperature range of K408F (K408C) to 4008F (2048C). Fluoroelastomers provide excellent resistance to oils, fuels, lubricants, most mineral acids, many aliphatic and aromatic hydrocarbons (carbon tetrachloride, benzene, toluene, and xylene) that act as solvents for chlorinated solvents, and pesticides. Special formulations can be produced to obtain resistance to hot mineral acids, steam, and hot water. These elastomers are not suitable for use with low-molecular-weight esters and ketones, certain amines, and hot anhydrous hydrofluoric or



147

chlorosulfonic acids. Their solubility in low-molecular-weight ketones is an advantage in producing solution coatings of fluoroelastomers. Refer to Table 4.21 for the compatibility of fluoroelastomers with selected corrodents and Reference [1] for additional listings. The chemical stability of these elastomers is an important property for their use as protective linings. Applications include linings for power station stacks operated with high sulfur fuels, and tank linings for the chemical industry. 4.10.19 Polyvinylidene Fluoride Polyvinylidene Fluoride (PVDF) is a homopolymer of 1:1 difluoroethane with alternating CH2 and CF2 groups along the polymer chain. These groups impart a unique polarity that influences its solubility. The polymer has the characteristic stability of fluoropolymers when exposed to aggressive chemical and thermal conditions. PVDF is manufactured under the tradename of Kynar by Elf Atochem, Solef by Solvay, Hylar by Ausimont U.S.A., and Super Pro and ISO by Asahi/Amarica. PVDF can be used in applications intended for repeated contact with food per Title 21, Code of Federal Regulations Chapter 1. Part 177.2520. It is also permitted for use in processing or storage areas in contact with meat or poultry food products prepared under federal inspection according to the U.S. Department of Agriculture (U.S.D.A.). Use is also permitted under “3-A Sanitary Standards for Multiple-Use Plastic Materials Used as Product Contact Surfaces for Dairy Equipment” Serial No. 2000. PVDF linings have an operating temperature range from K48F (K208C) to 2808F (1388C). Coating thickness range from 0.010 to 0.040 in. Polyvinylidene fluoride is resistant to most acids, alkalies, aliphatic and aromatic hydrocarbons, alcohols, and strong oxidizing agents. Highly polar solvents, such as acetone, and ethyl acetate may cause swelling. When used with strong alkalies, stress cracking results. Refer to Table 4.22 for the compatibility of PVDF with selected corrodents and Reference [1] for a more complete listing. Typical applications include lining vessels, agitators, pump housings, centrifuge housings, piping, and dust collectors. Previously glass-lined tanks and accessories can be refurbished with PVDF. 4.10.20 Isophthalic Polyester The isophthalic polyesters use isophthalic acid in place of phthalic anhydrides as the saturated monomer. This increases the cost of production but improves the chemical resistance. The standard corrosion-grade isophthalic polyesters are made with a 1:1 molar ratio of maleic anhydride or fumaric acid with propylene glycol.


148

Corrosion of Linings and Coatings TABLE 4.21 Compatibility of Fluoroelastomers with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aq. Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide

8F

8C

X 210 190 180 180 X X X 400 X X 190 190 100 190 180 400 400 190 400 X 390 X 140 190 400 300 300 140 140 190 190 X 140 180 180 X X 200 190 230 190 190 250 400 400

X 99 88 82 82 X X X 204 X X 88 88 38 88 82 204 204 88 204 X 199 X 60 88 204 149 149 60 60 88 88 X 60 82 82 X X 93 88 110 88 88 121 204 204 (continued)



149

TABLE 4.21 Continued Maximum Temperature Chemical Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry, 25% Bromine gas, moist, 25% Bromine liquid Butadiene Butyl acetate Butyl alcohol n-Butylamine Butyl phthalate Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium sulfate Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50%

8F

8C

400 400 X 400 190 400 400 400 190 400 180 180 350 400 X 400 X 80 120 400 400 190 190 300 300 400 400 400 200 400 80 X 400 400 350 400 X X X 190 190 190 400 400 X 350 350

204 204 X 204 88 204 204 204 88 204 82 82 177 204 X 204 X 27 49 204 204 88 88 149 149 204 204 204 93 204 27 X 204 204 177 204 X X X 88 88 88 204 204 X 177 177 (continued)


150

Corrosion of Linings and Coatings TABLE 4.21 Continued Maximum Temperature Chemical

8F

8C

Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc.

300 400 X 190 400 400 400 X 180 180 400 400 190 400 400 400 400 180 210 X X 400 400 400 350 350 400 210 350 X 400 190 X 300 400 390 390 180 190 X X 350 400 400 190 190 90

149 204 X 88 204 204 204 X 82 82 204 204 88 204 204 204 204 82 99 X X 204 204 204 177 177 204 99 177 X 204 88 X 149 204 199 199 82 88 X X 149 204 204 88 88 32 (continued)



151

TABLE 4.21 Continued Maximum Temperature Chemical Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

8F

8C

190 400 400 210 300 400 190 300 190 400 X X X 400 400 190 400 400 350 350 350 350 350 180 200 400 X 400 190 190 400

88 204 204 99 149 204 88 149 88 204 X X X 204 204 88 204 204 149 149 149 149 149 82 93 204 X 204 88 88 204


The isophthalic polyesters are the most common type used for chemical service applications. They have a wide range of corrosion resistance, being satisfactory for use up to 1258F (528C) in such acids as 10% acetic, benzoic, citric, oleic, 25% phosphoric, 10 to 25% sulfuric, and fatty acids. Most inorganic salts are compatible with isophthalic polyesters. Solvents such as amyl alcohol, ethylene glycol, formaldehyde, gasoline, kerosene, and naphtha are also compatible.


152

Corrosion of Linings and Coatings TABLE 4.22 Compatibility of PVDF with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aq. Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide

8F

8C

150 90 300 300 190 190 100 X 120 150 130 280 200 200 180 250 300 270 300 260 300 290 300 270 250 280 280 280 280 280 280 280 280 280 280 280 280 280 280 190 280 280 200 150 130 280 280 280

66 32 149 149 88 88 38 X 49 66 54 138 93 93 82 121 149 132 149 127 149 143 149 132 121 138 138 138 138 138 138 138 138 138 138 138 138 138 138 88 138 138 93 66 54 138 138 138 (continued)



153

TABLE 4.22 Continued Maximum Temperature Chemical Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol n-Butylamine Butyl phthalate Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chloride gas, dry Chlorine gas, wet, 10% Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50%

8F

8C

280 280 120 150 100 250 280 280 280 280 210 210 140 280 140 280 X 80 230 280 280 280 280 280 270 280 280 280 250 280 220 80 280 280 80 280 280 280 280 200 210 210 210 210 220 250 110 220 250

138 138 49 66 38 121 138 138 138 138 99 99 60 138 60 138 X 27 110 138 138 138 138 138 132 138 138 138 121 138 104 27 138 138 27 138 138 138 138 93 99 99 99 99 104 121 43 104 121 (continued)


154

Corrosion of Linings and Coatings TABLE 4.22 Continued Maximum Temperature Chemical Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichlorethane (ethylene dichloride) Dichloroacetic acid Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferrous chloride Ferrous nitrate Ferrous nitrate, 10–50% Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 20% Nitric acid, 5% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc.

8F

8C

110 250 250 250 250 280 280 280 210 270 270 250 210 280 120 280 280 280 280 280 280 80 80 280 280 260 280 280 280 260 200 200 280 250 110 130 110 280 250 280 X X 110 280 180 200 120 150 210

43 121 121 121 121 138 138 138 99 132 132 121 99 138 49 138 138 138 138 138 138 27 27 138 138 127 138 138 138 127 93 93 138 121 43 54 43 138 121 138 X X 43 138 82 93 49 66 99 (continued)



155

TABLE 4.22 Continued Maximum Temperature Chemical Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc.a Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid. 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

8F

8C

X 210 120 200 220 80 280 220 250 280 280 230 220 150 280 280 280 280 280 250 220 220 210 140 X X 220 X X 130 80 260

X 99 49 93 104 27 138 104 121 138 138 110 104 66 138 138 138 138 138 121 104 104 99 60 X X 104 X X 54 27 127

The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. A blank space indicates that the data is unavailable. a

Subject to stress corrosion cracking.


The isophthalic polyesters are not resistant to acetone, amyl acetate, benzene, carbon disulfide, solutions of alkaline salts of potassium and sodium, hot distilled water, or higher concentrations of oxidizing acids. Refer to Table 4.23 for the compatibility of isophthalic polyesters with selected corrodents and Reference [1] for a more complete listing.


156

Corrosion of Linings and Coatings TABLE 4.23 Compatibility of Isophthalic Polyester with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aq. Aluminum chloride, dry Aluminum fluoride, 10% Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonia gas Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate

8F

8C

X 180 110 X X X X X X X 220 X X 250 180 170 140 160 160 180 90 X 160 160 180 90 90 X X 160 160 160 180 X X X 160 X X 160 X 190 140 X 160

X 82 43 X X X X X X X 104 X X 121 82 77 60 71 71 82 32 X 71 71 82 32 32 X X 11 71 71 82 X X X 71 X X 71 X 88 60 X 71 (continued)



157

TABLE 4.23 Continued Maximum Temperature Chemical Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butyl acetate Butyl alcohol n-Butylamine Butyric acid, 25% Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite, 10% Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid, 50% water Chloride gas, dry Chlorine gas, wet Chlorine, liquid Chloroacetic acid, 25% Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride

8F

8C

90 X X 180 180 X X 140 180 X X X X 80 X 129 160 150 160 160 180 160 160 120 140 160 160 160 X 160 160 X 160 X 160 X X 160 160 X 150 X X X X X 140

32 X X 82 82 X X 60 82 X X X X 27 X 49 71 66 71 71 82 71 71 49 60 71 71 71 X 71 71 X 71 X 71 X X 71 71 X 66 X X X X X 60 (continued)


158


8F

8C

Citric acid, 15% Citric acid, conc. Copper acetate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Ketones, general Lactic acid, 25% Magnesium chloride Malic acid Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80%

160 200 160 180 160 200 X 170 170 80 X X 120 180 160 180 180 160 X X 120 140 140 160 160 90 X X X 90 X 160 180 90 X X 160 120 X X X 120 X X X X 180

71 93 71 82 71 93 X 77 77 27 X X 49 82 71 82 82 71 X X 49 60 60 71 71 32 X X X 32 X 71 82 32 X X 71 49 X X X 49 X X X X 82 (continued)



159

TABLE 4.23 Continued Maximum Temperature Chemical Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate, 20% Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid, 50% White liquor Zinc chloride

8F

8C

X 160 100 90 200 X X X X X X 180 180 160 150 X X X X X X X 110 170 X 180

X 71 38 32 93 X X X X X X 82 82 71 66 X X X X X X X 43 77 X 82


Applications include coating of chemical storage tanks. In food contact applications these resins withstand acids and corrosive salts encountered in foods and food handling. 4.10.21 Bisphenol-A Fumurate Polyesters This is a premium-grade corrosion resistant resin. It costs approximately one-third more than an isophthalic resin. Standard bisphenol-A fumurate resins are derived from the propylene glycol or oxide diether of bisphenol-A and fumuric acid. The aromatic


160


structure contributed by the bisphenol-A provides several benefits. Thermal stability is improved, and because the number of interior chain ester groups is reduced, the resistance to hydrolysis and saponification increases. Bisphenol-A polyesters have the best hydrolysis resistance of any commercial unsaturated polyester. The bisphenol polyesters are superior in their corrosion resistant properties to the isophthalic polyesters. They show good performance with moderate alkaline solutions, and excellent resistance to the various categories of bleaching agents. The bisphenol polyesters will break down in highly concentrated alkalies. These resins can be used in the handling of the following materials.

Acetic Benzoic Boric Butyric Chloroacetic, 15% Chromic, 5% Citric All aluminum salts Most ammonium salts Zinc salts Ammonium hydroxide, 5% to 1608F (718C) Calcium hydroxide, 25% to 1608F (718C) Sodium hydrosulfite, to 2008F (938C) Sour crude oil Linseed oil Carbon dioxide Sulfur trioxide Sulfur dioxide, dry

Acids, to 2008F (938C) Fatty acids Hydrochloric, 10% Lactic Maleic Oleic Oxalic Phosphoric, 80% Salt solutions to 2008F (938C) Cadmium salts Most plating solutions Alkalies Calcium hypochlorite, 208F to 2008F (938C) Chlorine dioxide, 15% to 2008F (938C)

Glycerine

Solvents

Gases, to 2008F (938C) Chlorine, wet Carbon monoxide

Stearic Sulfonic, 30% Tannic Tartaric Trichloroacetic, 50% Rayon spin bath

Copper salts Iron salts

Potassium hydroxide, 25% to 1608F (718C) Sodium chlorite, to 2008F (938C)

Alcohols at ambient temperatures Rayon waste gases, 1508F (658C)

Solvents such as benzene, carbon disulfide, ether methyl ethyl ketone, toluene, xylene, trichloroethylene, and trichloroethane will attack the resin. Sulfuric acid above 70% sodium hydroxide, and 30% chromic acid will also attack the resin. Refer to Table 4.24 for the compatibility of bisphenol-A fumurate resin with selected corrodents and Table 4.25 for the compatibility of hydrogenated bisphenol-A fumarate polyester resin. Reference [1] provides additional listings for both resins.



161

TABLE 4.24 Compatibility of Bisphenol-A Fumarate Polyester with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aq. Aluminum fluoride, 10% Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonia gas Ammonium carbonate Ammonium chloride 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 20% Ammonium hydroxide, 25% Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide

8F

8C

X 220 160 160 X 110 X X 100 X 220 X X 220 200 90 160 200 200 200 90 200 220 220 180 120 140 100 220 180 80 220 110 80 80 200 X X 220 X 200 220 150 220 140

X 104 171 171 X 43 X X 38 X 104 X X 104 93 32 71 93 93 93 32 93 104 104 82 49 60 38 104 82 27 104 43 27 27 93 X X 104 X 93 104 66 104 60 (continued)


162

Corrosion of Linings and Coatings TABLE 4.24 Continued Maximum Temperature Chemical Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine, liquid Butyl acetate Butyl alcohol n-Butylamine Butyric acid Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite, 10% Calcium nitrate Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chloroacetic acid, 50% water Chloroacetic acid, to 25% Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate

8F

8C

X X 200 180 X X 220 220 90 100 X 80 80 X 220 180 210 200 220 180 160 80 220 220 160 X 350 210 X 350 110 90 140 200 200 X 140 80 X X X X X 150 220 220 180

X X 93 82 X X 104 104 32 38 X 27 27 X 93 82 99 93 104 82 71 27 93 93 71 X 177 99 X 177 43 32 60 93 93 X 60 27 X X X X X 66 104 104 82 (continued)



163

TABLE 4.24 Continued Maximum Temperature Chemical

8F

8C

Copper chloride Copper cyanide Copper sulfate Cresol Cyclohexane Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, moist Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hypochlorous acid, 20% Iodine solution, 10% Lactic acid, 5% Lactic acid, conc. Magnesium chloride Malic acid Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Oleum Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium sulfide, to 50%

220 220 220 X X 100 X 220 220 220 220 220 220 220 220 160 220 190 X 200 90 90 200 210 220 220 160 X X 130 160 100 X X X X 220 110 200 150 160 220 130 220 200 X 210

104 104 104 X X 38 X 104 104 104 104 104 104 104 104 71 104 88 X 93 32 32 104 99 104 104 71 X X 54 71 38 X X X X 104 43 93 66 71 104 54 104 93 X 99 (continued)


164

Corrosion of Linings and Coatings TABLE 4.24 Continued Maximum Temperature Chemical Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid, 50% White liquor Zinc chloride

8F

8C

200 220 220 220 160 X X X X 110 X X 180 180 250

93 104 104 104 71 X X X X 43 X X 82 82 121


4.10.22 Halogenated Polyesters Halogenated resins consist of chlorinated or brominated polyesters. The chlorinated polyester resins cured at room temperature are also known as chlorendic polyesters. These resins have the highest heat resistance of any of the polyesters. They are also inherently fire retardant. A combustible rating of 20 can be achieved, making this the safest possible polyester for stacks, hoods, or wherever a fire hazard exists. Refer to Table 4.26 for the performance of chlorinated polyesters at elevated temperatures. This permits them to survive high-temperature upsets in flue gas desulfurization scrubbers, some of which can reach a temperature of 4008F (2048C). The halogenated polyesters exhibit excellent resistance in contact with oxidizing acids and solutions such as 35% nitric acid at room temperature, 40% chromic acid, chlorine water, wet chlorine, and 15% hypochlorites. They also resist neutral and acid salts, nonoxidizing acids, organic acids, mercaptans, ketones, aldehydes, alcohols, organic esters, and fats and oils. These polyesters are not resistant to highly alkaline solutions of sodium hydroxide, concentrated sulfuric acid, alkaline solutions with a pH greater than 10, aliphatic, primary, and aromatic amines, amides and other alkaline



165

TABLE 4.25 Compatibility of Hydrogenated Bisphenol A Fumarate Polyester with Selected Corrodents Maximum Temperature Chemical Acetic acid, 10% Acetic acid, 50% Acetic anhydride Acetone Acetyl chloride Acrylonitrile Aluminum acetate Aluminum chloride, aq. Aluminum fluoride Aluminum sulfate Ammonium chloride, sat. Ammonium nitrate Ammonium persulfate Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Benzaldehyde Benzene Benzoic acid Benzyl alcohol Benzyl chloride Boric acid Bromine, liquid Butyl acetate n-Butylamine Butyric acid Calcium bisulfide Calcium chlorate Calcium chloride Calcium hypochlorite, 10% Carbon bisulfide Carbon disulfide Carbon tetrachloride Chlorine gas, dry Chlorine gas, wet Chloroacetic acid, 50% water Chloroform Chromic acid, 50%

8F

8C

200 160 X X X X

93 71 X X X X

200 X 200 200 200 200 100 X 200 90 X 80 X 180 200 X X 210 X X 210 X X X X 120 210 210 180 X X X 210 210 90 X X

93 X 93 93 93 93 38 X 93 32 X 27 X 82 93 X X 99 X X 99 X X X X 49 99 99 82 X X X 99 99 32 X X (continued)


166


8F

8C

Citric acid, 15% Citric acid, conc. Copper acetate Copper chloride Copper cyanide Copper sulfate Cresol Cyclohexane Dichloroethane (ethylene dichloride) Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 50% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Lactic acid, 25% Lactic acid, conc. Magnesium chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Sodium carbonate, 10% Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 10% Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98%

200 210 210 210 210 210 X 210 X 210 200 200 210 210 90 90 180 190 X X 210 X X 210 210 210 X X 190 90 X X X X 210 100 210 100 X X 160 210 210 90 X X

93 99 99 99 99 99 X 99 X 99 93 93 99 99 32 32 82 88 X X 99 X X 99 99 99 X X 88 32 X X X X 99 38 99 38 X X 71 99 99 32 X X (continued)



167

TABLE 4.25 Continued Maximum Temperature Chemical Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid, 25% Toluene Trichloroacetic acid Zinc chloride

8F

8C

X X 210 90 90 200

X X 99 32 32 93


TABLE 4.26 General Application Guide for Chlorinated Polyesters Environment Acid halides Acids, mineral nonoxidizing Acids, organic Alcohols Aldehydes Alkaline solutions pHO10 Amines, aliphatic, primary aromatic Amides, other alkaline organics Esters, organic Fats and oils Glycols Ketones Mercaptans Phenol Salts, acid Salts, neutral Water, demineralized, distilled, deionized, steam and condensate

Comments Not recommended Resistant to 2508F/1218C Resistant to 2508F/1218C; glacial acetic acid to 1208F/498C Resistant to 1808F/828C Resistant to 1808F/828C Note recommended for continuous exposure Can cause severe attack Can cause severe attack Resistant to 1808F/828C Resistant to 2008F/958C Resistant to 1808F/828C Resistant to 1808F/828C Resistant to 1808F/828C Not recommended Resistant to 2508F/1218C Resistant to 2508F/1218C Resistant to 2128F/1008C; lowest absorption of any polyester


168

Corrosion of Linings and Coatings TABLE 4.27 Compatibility of Halogenated Polyesters with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, 10% Acetic acid, 50% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum, 10% Aluminum chloride, aq. Aluminum fluoride, 10% Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride, 50% Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide

8F

8C

X 140 90 110 100 X X X X 220 X X 200 120 90 170 160

X 60 32 43 38 X X X X 104 X X 93 49 32 77 71

250 150 140 200 200 200 140 140 90 90 200 140 150 200 120 100 190 200 X 120 200 X 250 250 X 180 X

121 66 60 93 93 93 60 60 32 32 93 60 66 93 49 38 85 93 X 49 93 X 121 121 X 82 X (continued)



169

TABLE 4.27 Continued Maximum Temperature Chemical Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine, liquid Butyl acetate Butyl alcohol n-Butylamine Butyric acid, 20% Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, sat. Calcium hypochlorite, 20% Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chloroacetic acid, 25% Chloroacetic acid, 50% water Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc.

8F

8C

X 90 120 250 X X 190 180 100 100 X 80 100 X 200 X 150 210 250 250 X 80 220 150 250 140 X 250 250 X 170 120 160 80 200 220 X 90 100 X X X 180 140 210 250 250

X 32 49 121 X X 88 82 38 38 X 27 38 X 93 X 66 99 121 121 X 27 104 66 121 60 X 121 121 X 77 49 71 27 93 104 X 32 38 X X X 82 60 99 121 121 (continued)


170


8F

8C

Copper acetate Copper chloride Copper cyanide Copper sulfate Cresol Cyclohexane Dibutyl phthalate Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrobromic acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 10% Hydrofluoric acid, 30% Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid, 10% Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 20% Nitric acid, 5% Nitric acid, 70% Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol, 5% Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate, 10% Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50%

210 250 250 250 X 140 100 100 X 250 250 250 250 250 160 160 200 200 230 180 150 100 120 200 200 250 90 80 X 80 190 80 210 80 90 X 90 90 90 250 100 230 130 190 250 110 X

99 121 121 121 X 60 38 38 X 121 121 121 121 121 71 71 93 93 110 82 66 38 49 93 93 121 32 27 X 27 88 27 99 27 32 X 32 32 32 121 38 110 54 88 121 43 X (continued)



171

TABLE 4.27 Continued Maximum Temperature Chemical Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 100% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, fuming Sulfurous acid, 10% Thionyl chloride Toluene Trichloroacetic acid, 50% White liquor Zinc chloride

8F

8C

X X X X 80 250 260 X 200 190 X X X 80 X 110 200 X 200

X X X X 27 121 127 X 93 88 X X X 27 X 43 93 X 93


organics, phenol, and acid halides. Table 4.27 lists the compatibility of halogenated polyesters with selected corrodents. Reference [1] provides additional information. Halogenated polyesters are widely used in the pulp and paper industry in bleach atmospheres. 4.10.23 Silicones The silicone systems are quite expensive, being based on organic silicone compounds (which have silicon rather than carbon linkages in the structure). They are primarily used for high-temperature service, where carbon-based linings would oxidize. Typically, the silicon atoms will have one or more side groups attached to K K them, generally phenol (C6HK 5 ), methyl (CH3 ), or vinyl (CH2aCH ) units. These groups impart properties such as solvent resistance, lubricity, and reactivity with organic chemicals and polymers. Because these side groups affect the corrosion resistance of the resin, it is necessary to verify with the supplier the properties of the resin being supplied.


172


The maximum allowable operating temperature is 5728F (3008C). These resins are available for operation at cryogenic temperatures. A second high-temperature formulation with aluminum can be operated up to 12008F (6498C). This high-temperature type requires baking for a good cure. It is also water repellent. The silicone resins can be used in contact with dilute acids and alkalies, alcohols, animal and vegetable oils, and lubrication oils. They are also resistant to aliphatic hydrocarbons, but aromatic solvents such as benzene, toluene, gasoline, and chlorinated solvents will cause excessive swelling. Table 4.28 lists the corrosion resistance of methyl appended silicone with selected corrodents. Reference [1] provides additional listings. TABLE 4.28 Compatibility of Methyl-Appended Silicone with Selected Corrodents Maximum Temperature Chemical Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetone Acrylic acid, 75% Acrylonitrile Alum Aluminum sulfate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium nitrate Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Benzene Benzyl chloride Boric acid Butyl alcohol Calcium bisulfide Calcium chloride Calcium hydroxide, 30% Calcium hydroxide, sat. Carbon bisulfide

8F

8C

90 90 90 90 100 80 X 220 410 X 80 80 80 X 210 80 X X X 80 X X X 390 80 400 300 200 400 X

32 32 32 32 43 27 X 104 210 X 27 27 27 X 99 27 X X X 27 X X X 189 27 204 149 93 204 X (continued)



173

TABLE 4.28 Continued Maximum Temperature Chemical Carbon disulfide Carbon monoxide Carbonic acid Chlorobenzene Chlorosulfonic acid Ethylene glycol Ferric chloride Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrofluoric acid, 30% Lactic acid, all conc. Lactic acid, conc. Magnesium chloride Methyl alcohol Methyl ethyl ketone Methyl isobutyl ketone Nitric acid, 20% Nitric acid, 5% Nitric acid, 70% Nitric acid, anhydrous Oleum Phenol Phosphoric acid, 50–80% Propyl alcohol Sodium carbonate Sodium chloride, 10% Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium sulfate Stannic chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Tartaric acid Tetrahydrofuran Toluene Tributyl phosphate Turpentine Vinegar

8F

8C

X 400 400 X X 400 400 X 90 X X 80 80 400 410 X X X 80 X X X X X 400 300 400 90 90 90 X 400 80 X X X X X X X X 400 X X X X 400

X 204 204 X X 204 204 X 32 X X 27 27 204 210 X X X 27 X X X X X 204 149 204 27 27 27 X 204 27 X X X X X X X X 204 X X X X 204 (continued)


174

Corrosion of Linings and Coatings TABLE 4.28 Continued Maximum Temperature Chemical Water, acid mine Water, demineralized Water, distilled Water, salt Water, sea Xylene Zinc chloride

8F

8C

210 210 210 210 210 X 400

99 99 99 99 99 X 204

The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature. Incompatibility is shown by an X. Source: From P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.

The silicones are used primarily as linings for high-temperature exhaust stacks, ovens, and space heaters.

References 1. 2. 3. 4.

P.A. Schweitzer. 2004. Corrosion Resistance Tables, 5th ed., vols. 1–4, New York: Marcel Dekker. J.S. Fry, C.N. Merriam, and W.H. Boyd. 1985. Chemistry and technology of phenolic resins and coatings, in Symposium Series Applied Polymer Science, Washington, DC: American Chemical Society. R.T. Morrison and R.N. Boyd. 1973. Organic Chemistry, 3rd ed., Boston: Allyn Bacon. P.A. Schweitzer. 2000. Mechanical and Corrosion Resistant Properties of Plastics and Elastomers, New York: Marcel Dekker.


5 Comparative Resistance of Organic Linings

Following is a series of tables comparing the corrosion resistance of various organic lining materials in contact with commonly used corrodents. The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature for which data is available. An “X” shows incompatibility. A blank space indicates that data is unavailable. One must keep in mind that most of the lining materials listed are capable of being formulated to meet specific conditions. In the tables, when a lining material is listed as satisfactory, it means that at least one formulation is acceptable. Therefore, before being used the manufacturer should be contacted to be sure that his formulation will be compatible with the application. More extensive listings will be found in Reference [1].

175


176

Corrosion of Linings and Coatings Acetic Acid, 10% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

212 (100) 190 (88) 212 (100) 200 (93) X 100 (38) 90 (32) 160 (71) 80 (27) 200 (93) 100 (38) 450 (232) 400 (204) 450 (232) 250 (121) 250 (121) 190 (88) 300 (149) 180 (82) 220 (104) 200 (93) 140 (60) 90 (32)


Comparative Resistance of Organic Linings

177

Acetic Acid, 50% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy, 20% Coal tar Urethanes, 20% Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

110 (43) 160 (71) 180 (82) X 100 (38) 90 (32) 160 (71) 80 (27) 200 (93) 90 (32) 450 (232) 400 (204) 450 (232) 250 (121) 250 (121) 180 (82) 300 (149) 110 (43) 160 (71) 160 (71) 90 (32) 90 (32)


178

Corrosion of Linings and Coatings Acetic Acid, 80% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

110 (43) 80 (27) 150 (66) X

160 (71) 80 (27) 200 (93) X 450 (232) 400 (204) 450 (232) 230 (110) 150 (66) 180 (82) 190 (88) X 160 (71) 90 (32)



179

Acetic Acid, Glacial Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

70 (21) 80 (27) 150 (66) X

X 80 (87) X X 450 (232) 400 (204) 450 (232) 230 (110) 200 (93) X 190 (88) X X 110 (43) 90 (32)


180

Corrosion of Linings and Coatings Acetic Acid, Vapors Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters, 50% Bisphenol A fumurate Hydrogenated polyester Halogenated polyester, 25% Methyl-appended silicone

110 (43) X X 100 (38) 90 (32) 90 (32) 90 (32) 90 (32) X 200 (93) 400 (204) 400 (204) 200 (93) 90 (32) 180 (82) 110 (43) 180 (82)



181

Acetic Anhydride Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 200 (93) 100 (38) X X X 200 (93) 200 (93) X 200 (93) 400 (202) 450 (232) 300 (149) 100 (38) X 100 (38) X 100 (38) X 100 (38)


182

Corrosion of Linings and Coatings Acetone Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 110 (43) 80 (27) X X X X 90 (32) X 80 (27) X X 450 (232) 400 (204) 450 (232) 150 (66) 150 (66) X X X X X X 100 (43)



183

Ammonium Carbonate Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

90 (32) 140 (60) 240 (116) 150 (66)

200 (93) 140 (60) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 190 (88) 280 (138) X 90 (32) 140 (60)


184

Corrosion of Linings and Coatings Ammonium Hydroxide, 25% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate, 20% Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 140 (60) 250 (121) 100 (38) 100 (38) 110 (43) 90 (32) 200 (93) X 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 190 (88) 280 (138) X 140 (60) 90 (32) X



185

Ammonium Hydroxide, Sat. Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 150 (66) 200 (93) 130 (54)

200 (93) X 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 190 (88) 280 (138) X 90 (32) X


186

Corrosion of Linings and Coatings Aniline Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 150 (66) 80 (27) X

X 140 (60) X 450 (232) 400 (204) 450 (232) 230 (110) 90 (32) 230 (110) 200 (93) X X X 120 (49) X



187

Benzoic Acid Maximum Temperature 8F (8C) Phenolics, 10% Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

100 (38) 200 (93) 260 (127) 180 (82) 100 (38) 100 (38) X 150 (66) 150 (66) 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 270 (132) 250 (121) 400 (204) 250 (121) 180 (82) 180 (82) 210 (99) 250 (121)


188

Corrosion of Linings and Coatings Bromine Gas, Dry Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers, 25% PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 100 (38) X 100 (38) X X 60 (16) X 450 (232) 200 (93) 450 (232) 150 (66) X 180 (82) 210 (99) X 90 (32) 100 (38)



189

Bromine Gas, Moist Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers, 25% PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 100 (38) X X X X 60 (16) X 200 (93) 200 (93) 250 (121) 180 (82) 210 (99) X 100 (38) 100 (38)


190

Corrosion of Linings and Coatings Bromine, Liquid Maximum Temperature 8F (8C) Phenolics Epoxy Furans, 3% max Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters, 50% Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 300 (149) X

X 60 (16) X 450 (232) 400 (204) 450 (232) 150 (66) 350 (177) 140 (60) X X X X



191

Calcium Hydroxide Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 180 (32) 260 (170) 180 (82) 140 (60) 100 (38) X 90 (32) 230 (110) X 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 400 (204) 280 (138) 160 (71) 160 (71) X 400 (201)


192

Corrosion of Linings and Coatings Carbon Tetrachloride Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 170 (77) 212 (100) 180 (82) 212 (100) X X X X 200 (93) X 450 (232) 400 (204) 450 (232) 270 (132) 300 (149) 350 (177) 280 (138) X 110 (43) X 120 (49) X



193

Chlorine Gas, Wet Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF, 10% Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 250 (121) 250 (121) X X X X X 90 (32) X 450 (232) 400 (204) 450 (232) 250 (121) 250 (121) 190 (88) 210 (99) 160 (71) 200 (93) 210 (99) 220 (104) X


194

Corrosion of Linings and Coatings Chlorine, Liquid Maximum Temperature 8F (8C) Phenolics Epoxy Furans, 3% max Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X X X

X X X 400 (204) X 250 (121) 190 (88) 210 (99) X X X X



195

Chlorobenzene Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

260 (127) 150 (66) 260 (127) 110 (43) 100 (38) 100 (38) X X X X X X 450 (232) 400 (204) 450 (232) 210 (99) 150 (66) 400 (204) 220 (104) X X X X


196

Corrosion of Linings and Coatings Chloroform Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 110 (43) X X X X X X X X X 450 (232) 400 (204) 450 (232) 230 (110) 250 (121) 400 (204) 250 (121) X X X X X



197

Chlorosulfonic Acid Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

140 (60) X 260 (127) X X X X X X X 60 (16) 450 (232) 400 (204) 450 (232) 80 (27) 80 (27) X 110 (43) X X X X


198

Corrosion of Linings and Coatings Citric Acid, 10% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 190 (88) 250 (121) 210 (99) 100 (38) 100 (38) 150 (66) X 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 120 (49) 300 (149) 300 (149) 250 (121) 160 (71) 220 (104) 200 (93) 250 (121) X



199

Citric Acid, Conc. Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Silicone

160 (71) X 250 (121) 200 (93) 100 (38) 100 (38) 200 (93) X 250 (121) 140 (60) 370 (188) 400 (204) 450 (232) 300 (149) 400 (204) 250 (121) 200 (93) 220 (104) 210 (99) 250 (121) 390 (199)


200

Corrosion of Linings and Coatings Dextrose Maximum Temperature 8F (8C) Phenolics Epoxy Furans, 3% max Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

100 (38) 260 (127) 240 (116) 100 (38) 100 (38) X 200 (93) 200 (93) 140 (60) 200 (93) 400 (204) 450 (232) 240 (116) 400 (204) 280 (138) 180 (82) 220 (104) 220 (104) 170 (77)



201

Dichloroacetic Acid Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols, 20% PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 100 (38) X X X 100 (38) 400 (204) 400 (204) 150 (66) 120 (49) X 100 (38) 100 (38)


202

Corrosion of Linings and Coatings Diesel Fuels Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

100 (38) 240 (116) 220 (104) 100 (38) 100 (38) 80 (27) 80 (27) 80 (27) 100 (38) 200 (93) 400 (204) 400 (204) 300 (149) 300 (149) 400 (204) 280 (138) 160 (71) 180 (82) 180 (82)



203

Diethylamine Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 200 (93) X X X X 120 (49) X X 200 (93) 400 (204) 400 (204) 200 (93) X X 100 (38) 120 (49) X X


204

Corrosion of Linings and Coatings Dimethyl Formamide Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X X X X X 160 (71) X X 200 (93) 400 (204) 450 (232) 250 (121) 100 (38) X X X X X X



205

Ethyl Acetate Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 200 (93) X X X X 90 (32) X 80 (27) 140 (60) X 200 (93) 400 (204) 400 (204) 150 (66) 150 (66) X 160 (71) X X X X


206

Corrosion of Linings and Coatings Ethyl Alcohol Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Silicone

110 (43) 140 (60) 140 (60) 100 (38) 100 (38) 100 (38) 90 (32) 200 (93) 150 (66) 200 (93) 140 (60) 200 (93) 200 (93) 400 (204) 300 (149) 300 (149) 300 (149) 280 (138) 80 (27) 90 (32) 90 (32) 140 (60) 400 (204)



207

Hydrobromic Acid, Dil. Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 180 (82) 212 (100) 180 (82) X X X X 90 (32) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 400 (204) 260 (127) 120 (49) 220 (104) 200 (93) X


208

Corrosion of Linings and Coatings Hydrobromic Acid, 20% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 180 (82) 212 (100) 180 (82) X X X X 100 (38) 190 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 400 (204) 280 (138) 140 (60) 220 (104) 90 (32) 160 (71) X



209

Hydrobromic Acid, 50% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 110 (43) 212 (100) 200 (93) X X X X 100 (38) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 400 (204) 280 (138) 140 (60) 160 (71) 90 (32) 200 (93) X


210

Corrosion of Linings and Coatings Hydrochloric Acid, Dil. Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

300 (149) 200 (93) 212 (100) 220 (104) 100 (38) 100 (38) X X X X 160 (71) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 350 (177) 280 (138) 160 (71) 190 (88) 180 (82) 230 (110) 90 (32)



211

Hydrochloric Acid, 20% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

300 (149) 200 (93) 212 (100) 220 (104) X X X X X X 160 (71) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 350 (177) 280 (138) 160 (71) 190 (88) 180 (82) 230 (110) 90 (32)


212

Corrosion of Linings and Coatings Hydrochloric Acid, 35% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

300 (149) 140 (60) 80 (27) 180 (82) X X X X X X 140 (60) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 350 (177) 280 (138) 160 (71) X 190 (88) 180 (82) X



213

Hydrofluoric Acid, 30% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 230 (110) X X X X X X 90 (32) 120 (49) 450 (232) 400 (204) 450 (232) 270 (132) 250 (121) 210 (99) 260 (127) X X 120 (49) X


214

Corrosion of Linings and Coatings Hydrofluoric Acid, 70% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 140 (60) X X X X X X 90 (32) 68 (20) 450 (232) 400 (204) 450 (232) 250 (121) 240 (116) 350 (177) 200 (93) X X X X



215

Hydrofluoric Acid, 100% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 140 (60) X X X X X X 90 (32) 450 (232) 400 (204) 450 (232) 230 (110) 240 (116) X 200 (93) X X X


216

Corrosion of Linings and Coatings Hypochlorous Acid, 100% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate, 20% Hydrogenated polyester, 50% Halogenated polyester, 10% Methyl-appended silicone

200 (93) X 150 (66) X X X X 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 400 (204) 280 (138) 90 (32) 90 (32) 210 (99) 100 (38)



217

Lactic Acid, 25% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 220 (104) 212 (100) 210 (99) X X X 140 (60) X 140 (60) 140 (60) 450 (232) 400 (204) 450 (232) 250 (121) 150 (66) 300 (149) 130 (54) 160 (71) 210 (99) 210 (99) 200 (93) X


218

Corrosion of Linings and Coatings Lactic Acid, Conc. Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 160 (71) 200 (93) X X X 90 (32) X 80 (27) 80 (27) 450 (232) 400 (204) 450 (232) 250 (121) 150 (66) 400 (204) 110 (43) 160 (71) 220 (104) 210 (99) 200 (93) X



219

Methyl Alcohol Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

140 (60) X 160 (71) 90 (32) 100 (38) 100 (38) 90 (32) 140 (60) 80 (27) 200 (93) 140 (60) 200 (93) 400 (204) 400 (204) 300 (149) 300 (149) X 200 (93) X 140 (60) 140 (60) 410 (210)


220

Corrosion of Linings and Coatings Methyl Cellosolve Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

100 (38) 80 (27) X X

200 (93) X 190 (88) 400 (204) 400 (204) 300 (149) 300 (149) X 280 (138)

X



221

Methyl Chloride Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

300 (149) X 120 (49) X X X X X 140 (60) X X 200 (93) 400 (204) 400 (204) 300 (149) 300 (149) 190 (88) 300 (149)

80 (27)


222

Corrosion of Linings and Coatings Methyl Ethyl Ketone Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 90 (32) 80 (27) X X X X X X X 450 (232) 400 (204) 450 (232) 230 (110) 150 (66) X X X X X X X



223

Methyl Isobutyl Ketone Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 140 (60) 160 (71) X X X X X X 80 (27) X X 450 (232) 400 (204) 450 (232) 300 (149) 150 (66) X 110 (43) X X X 80 (27) X


224

Corrosion of Linings and Coatings Methylene Chloride Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 280 (138) X X X X X X X X 200 (93) 400 (204) 400 (204) 210 (99) X X 120 (49) X X X X X



225

Naphtha Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

110 (43) 100 (38) 200 (93) 200 (93) 100 (38) 100 (38) 90 (32) X 80 (27) X 140 (60) 200 (93) 400 (204) 400 (204) 300 (149) 300 (149) 400 (204) 280 (138) 200 (93) 150 (66) 200 (93) 200 (93) X


226

Corrosion of Linings and Coatings Nitric Acid, 5% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 200 (93) 180 (82) X X X X X X 100 (38) 100 (38) 450 (232) 400 (204) 450 (232) 150 (66) 300 (149) 400 (204) 200 (93) 120 (49) 160 (71) 90 (32) 210 (99) 80 (27)



227

Nitric Acid, 20% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 100 (38) X 150 (66) X X X X X X 100 (38) 140 (60) 450 (232) 400 (204) 450 (232) 150 (66) 250 (121) 400 (204) 180 (82) X 100 (38) 80 (27) X


228


Nitric Acid, Dil. Coatings for Immersion Service Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic PE Bis. A fum. PE Hydrogenated PE Halogenated PE Silicone (methyl) Sodium silicate Potassium silicate Silica Furan Polyester Epoxy Vinyl ester Acrylic Urethane

Maximum Temperature 8F (8C) X 160 (71) 200 (93) 180 (82) X X X X X X 100 (38) 100 (38) 450 (232) 400 (204) 450 (232) 150 (66) 300 (149) 400 (204) 200 (93) 120 (49) 160 (71) 90 (32) 210 (99) 80 (27) Mortars 450 (232) 450 (232) 450 (232) X 140 (60) X 180 (82) X X

Paints (SZ Splash Resistant WZ Immersion Resistant) Acrylics Alkyds: Long oil Short oil Asphalt Chlorinated rubber Coal tar Coal tar epoxy Epoxies: Aliphatic polyamine Polyamide Polyamine Phenolic Polyesters Polyvinyl butyral Polyvinyl formal Silicone (methyl) Urethanes: Aliphatic Aromatic Vinyls Vinyl ester Zinc rioh


R, S

X R, W X X X X X X R R R R R, W R R


229

Nitric Acid, 70% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X X X X X X X X X X 70 (23) 450 (232) 400 (204) 450 (232) 80 (27) 150 (66) 190 (88) 120 (49) X X 80 (27) X


230

Corrosion of Linings and Coatings Nitric Acid, Conc. Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X X X X X X X X X X 60 (16) 450 (232) 400 (204) 450 (232) 210 (99) 250 (121) 90 (32) 210 (99) X X 90 (32) X



231

Nitrobenzene Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

80 (27) X 260 (127) 100 (38) X X X X X X X X 200 (93) 400 (204) 400 (204) 300 (149) 140 (60) X 140 (60) X X X X


232

Corrosion of Linings and Coatings Oil, Vegetable Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

90 (32) 260 (127) 180 (82) 100 (38) 100 (38) 240 (116) X 140 (60) 200 (93) 400 (204) 400 (204) 290 (143) 300 (149) 200 (93) 220 (104) 150 (66) 220 (104) 220 (104)



233

Oxalic Acid, 10% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 100 (38) 200 (93) 200 (93) 100 (38) 100 (38) 200 (93) X 200 (93) 140 (60) 400 (204) 400 (204) 200 (93) 140 (60) 400 (204) 140 (60) 160 (71) 200 (93) 200 (93) 200 (93)


234

Corrosion of Linings and Coatings Mineral Oil Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Silicone

160 (71) 210 (99) 250 (121) 100 (38) 100 (38) 90 (32) 200 (93) 80 (27) 200 (93) 140 (60) 200 (93) 400 (204) 400 (204) 300 (149) 300 (149) 400 (204) 250 (121) 200 (93) 200 (93) 90 (32) 300 (149)



235

Motor Oil Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 110 (43) 250 (121) 110 (43)

80 (27) 140 (60) 200 (93) 400 (204) 400 (204) 300 (149) 190 (88) 250 (121) 160 (71)


236

Corrosion of Linings and Coatings Oxalic Acid, Sat. Maximum Temperature 8F (8C) Phenolics (dry) Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

110 (43) 100 (38) 200 (93) 200 (93) 100 (38) 100 (38) X X X 140 (60) 400 (204) 400 (204) 200 (93) 140 (60) 400 (204) 120 (49) 160 (71) 200 (93) 200 (93) 200 (93)



237

Perchloric Acid, 10% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X 140 (60) X X X X X 90 (32) X 200 (93) 400 (204) 400 (204) 200 (93) 140 (60) 400 (204) 200 (93) X X X 90 (32) X


238

Corrosion of Linings and Coatings Perchloric Acid, 70% Maximum Temperature 8F (8C) Phenolics (dry) Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 200 (93) X X X X X X 90 (32) X 200 (93) 400 (204) 400 (204) 140 (60) 140 (60) 400 (204) 100 (38) X X X 90 (32) X



239

Phenol Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester, 5% Methyl-appended silicone

X X X X X X X X X X X X 450 (232) 400 (204) 450 (232) 210 (99) 150 (66) 210 (99) 200 (93) X X X 90 (32) X


240

Corrosion of Linings and Coatings Phosphoric Acid, 50–80% Maximum Temperature 8F (8C) Phenolics (dry) Epoxy Furans, 50% Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 110 (43) 212 (100) 210 (99) X X X 150 (66) X 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 270 (132) 250 (121) 300 (149) 220 (104) 180 (82) 220 (104) 210 (99) 250 (121) X



241

Phthalic Acid Maximum Temperature 8F (8C) Phenolics (dry) Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

100 (38) X 200 (93) 200 (93)

200 (93) 140 (60) X 400 (204) 400 (204) 200 (93) 200 (93) 90 (32) 200 (93) 160 (71) 200 (93) 200 (93) 80 (27)


242

Corrosion of Linings and Coatings Potassium Acetate Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 200 (93) 200 (93) 100 (38) 100 (38)

250 (121) 200 (93) 400 (204) 80 (27) 200 (93) 160 (71) 200 (93) 200 (93) X



243

Potassium Bromide, 30% Maximum Temperature 8F (8C) Phenolics, 10% Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 200 (93) 200 (93) 200 (93) 100 (38) 100 (38) 90 (32) 160 (71) 240 (116) 140 (60) 200 (93) 400 (204) 400 (204) 300 (149) 300 (149) 190 (88) 200 (93) 160 (71) 200 (93) 200 (93)


244

Corrosion of Linings and Coatings Potassium Carbonate, 50% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide, 25% Coal tar epoxy, 25% Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate, 10% Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 240 (116) 120 (49) 100 (38) 100 (38) 200 (93) 200 (93) 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 180 (82) 200 (93) X 180 (82) X 110 (43)



245

Potassium Chloride, 30% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Silicone

200 (93) 260 (127) 200 (93) 100 (38) 100 (38) 110 (43) 160 (71) 240 (116) 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 400 (204) 260 (127) 160 (71) 200 (93) 190 (88) 190 (88) 400 (204)


246

Corrosion of Linings and Coatings Potassium Cyanide, 30% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Silicone

200 (93) 260 (127) X 140 (60) 140 (60) 90 (32) 200 (93) 200 (93) 140 (60) 200 (93) 400 (204) 400 (204) 300 (149) 300 (149) 400 (204) 240 (116) X 200 (93) 200 (93) 140 (60) 400 (204)



247

Potassium Hydroxide, 50% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 100 (38) 200 (93) X 100 (38) 100 (38) 90 (32) 200 (93) 80 (27) 200 (93) 140 (60) 200 (93) 400 (204) 400 (204) 200 (93) 140 (60) X 200 (93) X 160 (71) X X


248

Corrosion of Linings and Coatings Potassium Hydroxide, 90% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

100 (38) 200 (93) X X X X 90 (32) 200 (93) 200 (93) 140 (60) 200 (93) 400 (204) 400 (204) 140 (60) X 200 (93) X X X X



249

Potassium Nitrate, 80% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 200 (93) 260 (127) 200 (93) 100 (38) 100 (38) 90 (32) 200 (93) 240 (116) 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 400 (204) 260 (127) 180 (82) 200 (93) 180 (82) 180 (82) 400 (204)


250

Corrosion of Linings and Coatings Potassium Permanganate, 10% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

80 (27) 140 (60) 260 (127) 200 (93) 100 (38) 100 (38) 100 (38) 100 (38) 240 (116) 140 (60) 200 (93) 400 (204) 460 (238) 280 (138) 280 (138) 160 (71) 260 (127) X 200 (93) 210 (99) 150 (66)



251

Potassium Permanganate, 20% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

90 (32) 140 (60) 160 (71) 100 (38) 100 (38) 100 (38) 240 (116) 90 (32) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 160 (71) 260 (127) 100 (38) 200 (93) 140 (60)


252

Corrosion of Linings and Coatings Potassium Sulfate, 10% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 240 (116) 200 (93) 100 (38) 100 (38) 90 (32) 200 (93) 90 (32) 240 (116) 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 400 (204) 260 (127) 100 (38) 200 (93) 200 (93) 190 (88)



253

Propylene Glycol Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 100 (38) 240 (116) 200 (93) 100 (38) 100 (38) 90 (32) X 400 (204) 400 (204) 400 (204) 300 (149) 240 (116) 180 (82) 200 (93) 200 (93) 100 (38)


254

Corrosion of Linings and Coatings Pyridine Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X X X X X X X X X 200 (93) 400 (204) 460 (238) 140 (60) X X X X X X X X



255

Salicylic Acid Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 240 (116) 140 (60) 100 (38) 100 (38) X X X 200 (93) 400 (204) 400 (204) 240 (116) 240 (116) 280 (138) 200 (93) 100 (38) 140 (60) 120 (49)


256

Corrosion of Linings and Coatings Sodium Acetate Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) 260 (127) 200 (93) 100 (38) 100 (38) 200 (93) X 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) X 260 (127) 180 (82) 180 (82) 200 (93) 200 (93) X



257

Sodium Bicarbonate, 20% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters, 10% Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Silicone

X 200 (93) 240 (116) 200 (93) 100 (38) 100 (38) 200 (93) 240 (116) 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 400 (204) 260 (127) 180 (82) 160 (71) 140 (60) 400 (204)


258

Corrosion of Linings and Coatings Sodium Bisulfate Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

260 (127) 200 (93) 240 (116) 200 (93) 100 (38) 100 (38) 200 (93) 100 (38) 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 180 (82) 260 (127) 180 (82) 200 (93) 200 (93)



259

Sodium Carbonate Maximum Temperature 8F (8C) Phenolics Epoxy Furans, 50% Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters, 20% Bisphenol A fumurate Hydrogenated polyester, 10% Halogenated polyester, 10% Methyl-appended silicone

160 (71) 200 (38) 240 (116) 180 (82) 100 (38) 100 (38) 200 (93) X 240 (116) 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 180 (82) 260 (127) 90 (32) 160 (71) 100 (38) 180 (82) 300 (149)


260

Corrosion of Linings and Coatings Sodium Chlorate Maximum Temperature 8F (8C) Phenolics, 50% Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy, 50% Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester, 48% Methyl-appended silicone

160 (71) 100 (38) 160 (71) 220 (104) 100 (38) 80 (27) 240 (116) 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 180 (82) 260 (127) X 200 (93) 200 (93) 200 (93)



261

Sodium Chloride Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone, 10%

160 (71) 200 (93) 240 (116) 180 (82) 110 (43) 110 (43) X 80 (27) 200 (93) 80 (27) 240 (116) 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 400 (204) 260 (127) 200 (93) 200 (93) 200 (93) 210 (99) 400 (204)


262

Corrosion of Linings and Coatings Sodium Cyanide Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester, 50% Silicone

200 (93) 240 (116) 200 (93) 100 (38) 100 (38) 180 (82) 240 (116) 140 (60) 200 (93) 400 (204) 400 (204) 280 (138) 280 (138) 400 (204) 260 (127) 150 (66) 160 (71) 140 (60) 140 (60)



263

Sodium Hydroxide, 10% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

300 (149) 190 (88) X 170 (77) 100 (38) 100 (38) 90 (32) 230 (110) X 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 230 (110) 300 (149) X 230 (110) X 130 (54) 100 (38) 110 (43) 90 (27)


264

Corrosion of Linings and Coatings Sodium Hydroxide, 50% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X 200 (93) X 220 (104) 100 (38) 100 (38) 90 (32) 230 (110) X 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 230 (110) 250 (121) X 220 (104) X 220 (104) X X 90 (27)



265

Sodium Hypochlorite, 20% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X X 180 (82) X X X X X 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 400 (204) 280 (138) X X 160 (71) X X


266

Corrosion of Linings and Coatings Sodium Hypochlorite, Conc. Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X X 100 (38) X X X X 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 300 (149) 400 (204) 280 (138) X X X X



267

Sodium Nitrate Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

80 (27) 200 (93) 160 (71) 200 (93) 80 (27) 90 (32) 200 (93) 140 (60) 140 (60) 200 (93) 400 (204) 400 (204) 300 (149) 300 (149) X 280 (138) 180 (82) 220 (104) 210 (99) 250 (121) X


268

Corrosion of Linings and Coatings Sodium Peroxide, 10% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

90 (32) 160 (71) X X X 200 (93) 250 (121) 140 (60) 200 (93) 400 (204) 400 (204) 300 (149) 300 (149) 400 (204) 260 (127) X 220 (104) X X



269

Stearic Acid Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

210 (99) 220 (104) 260 (127) 220 (104) X X X 90 (32) 200 (93) 140 (60) 140 (60) 200 (93) 400 (204) 400 (204) 300 (149) 300 (149) 100 (38) 280 (138) 180 (82) 200 (93) 210 (99) 250 (121) X


270

Corrosion of Linings and Coatings Styrene Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

100 (38) 360 (182) 100 (38) X X X X X 100 (38) 350 (177) 210 (99) 300 (149) 190 (88) X 100 (38) 100 (38) X X



271

Sulfur Dioxide, Wet Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

300 (149) 150 (66) 260 (127) 210 (99) 100 (38) 100 (38) X X X 200 (93) 400 (204) 400 (204) 230 (110) 150 (66) X 210 (99) 90 (32) 220 (104) 210 (99) 250 (121)


272

Corrosion of Linings and Coatings Sulfur Trioxide Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

300 (149) X 210 (99) X X X X X 140 (60) 200 (93) 400 (204) 400 (204) 80 (27) 80 (27) 190 (88) X 90 (32) 250 (121) 120 (49) X



273

Sulfuric Acid, 10% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

250 (121) 140 (60) 160 (71) 200 (93) X X X X 150 (66) X 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 250 (121) 350 (177) 250 (121) 180 (71) 220 (104) 210 (99) 260 (127) X


274

Corrosion of Linings and Coatings Sulfuric Acid, 50% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

250 (121) X 260 (127) 210 (99) X X X X 100 (38) X 200 (93) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 250 (121) 350 (177) 220 (104) 150 (66) 220 (104) 210 (99) 200 (93) X



275


210 (93) X 180 (82) X X X X X X 160 (71) 140 (60) 450 (232) 400 (204) 450 (232) 300 (149) 250 (121) 350 (177) 220 (104) X 160 (71) 90 (32) 190 (88) X


276

Corrosion of Linings and Coatings Sulfuric Acid, 90% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

X X X X X X X X X X X X 450 (232) 400 (204) 450 (232) 300 (149) 150 (66) 350 (177) 210 (99) X X X X X



277


X X X X X X X X X X X X 450 (232) 400 (204) 450 (232) 300 (149) 150 (66) 350 (177) 140 (60) X X X X X


278

Corrosion of Linings and Coatings Sulfuric Acid, 100% Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester, 50% Methyl-appended silicone

X X X X X X X X X X X X 450 (232) 400 (204) 450 (232) 300 (149) 80 (27) 180 (82) X X X X X X



279

Sulfurous Acid Maximum Temperature 8F (8C) Phenolics Epoxy, 20% Furans Vinyl ester, 10% Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester, 25% Halogenated polyester, 10% Methyl-appended silicone

X 240 (116) 160 (71) 120 (49) 110 (43) 100 (38) 100 (38) 160 (71) 140 (60) 450 (232) 400 (204) 450 (232) 210 (99) 250 (121) 400 (204) 220 (104) X 110 (43) 210 (99) 80 (27) X


280

Corrosion of Linings and Coatings Thionyl Chloride Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFAa FEPa PTFEa ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone a

200 (93) X X X

X X 450 (232) 400 (204) 450 (232) 210 (99) 150 (66) X X X X X

Corrodent will permeate.



281

Toluene Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

200 (93) X 212 (100) 120 (49) X X X X X X X X 200 (93) 400 (204) 400 (204) 250 (121) 140 (60) 400 (204) 210 (99) 100 (38) X 80 (27) 100 (38) X


282

Corrosion of Linings and Coatings Trichloroethylene Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) X 160 (71) X X X X X X X X X 200 (93) 400 (204) 400 (204) 270 (132) 300 (149) 400 (204) 260 (127) X X 120 (49) X



283

Turpentine Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

110 (43) 150 (66) 150 (66) X X X X X 80 (27) X X 200 (93) 400 (204) 400 (204) 270 (132) 300 (149) 400 (204) 280 (138) 80 (27) 80 (27) 120 (49) X


284

Corrosion of Linings and Coatings Water, Salt Maximum Temperature 8F (8C) Phenolics Epoxy, 10% Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 210 (99) 160 (71) 130 (54) 130 (54) 100 (38) X 210 (99) 80 (27) 250 (121) 140 (60) 200 (93) 400 (204) 400 (204) 250 (121) 300 (149) 190 (88) 280 (138) 160 (71) 180 (82) 210 (99) 210 (99)



285

White Liquor Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

160 (71) 200 (93) 140 (60) 180 (82) 150 (66) 100 (38) X X 140 (60) 140 (60) 400 (204) 400 (204) 250 (121) 190 (88) 200 (93) X 180 (82) X


286

Corrosion of Linings and Coatings Xylene Maximum Temperature 8F (8C) Phenolics Epoxy Furans Vinyl ester Epoxy polyamide Coal tar epoxy Coal tar Urethanes Neoprene Polysulfides Hypalon Plastisols PFA FEP PTFE ETFE ECTFE Fluoroelastomers PVDF Isophthalic polyesters Bisphenol A fumurate Hydrogenated polyester Halogenated polyester Methyl-appended silicone

150 (66) X 260 (127) 140 (60) X X X X X 80 (27) X X 200 (93) 400 (204) 400 (204) 250 (121) 150 (66) 400 (204) 210 (99) X 90 (32) 90 (32) 150 (66) X

Reference 1.

P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.


6 Sheet Linings

Designers of tanks and process vessels are faced with the problem of choosing the most reliable material of construction at a reasonable cost. When handling corrosive materials, a choice must often be made between using an expensive metallic material of construction or using a low-cost material from which to fabricate the shell and then installing a corrosionresistant lining. Carbon steel has been and still is the material predominantly selected; although, there has been a tendency over the past few years to use a fiberglass-reinforced plastic shell. This latter choice has the advantage of providing atmospheric corrosion protection of the shell exterior. For many years, vessels have been successfully lined with various rubber formulations, both natural and synthetic. Many such vessels have given over twenty years of reliable service. With the development of newer synthetic elastomeric and plastic materials, the variety of available lining materials has greatly increased. As with any material, the corrosion resistance, allowable operating values, and cost varies with each. Care must be taken when selecting the lining material that it is compatible with the corrodent being handled at the operating temperatures and pressures required.

6.1 A Shell Design For a lining to perform satisfactorily, the vessel shell must meet certain design configurations. Although these details may vary slightly depending on the specific lining material to be used, there are certain basic principles that apply in all cases: 1. Vessel must be of butt-welded construction. 2. All internal welds must be ground flush. 3. All weld spatter must be removed.

287


288


4. All sharp corners must be ground to a minimum of 1/8 in. radius. 5. All outlets to be of flanged or pad type. Certain lining materials require that nozzles be not less than 2 in. (55 mm) in diameter. 6. No protrusions are permitted inside of the vessel. Once the lining has been installed, there should be no welding permitted on the exterior of the vessel. After the fabrication has been completed, the interior surface of the vessel must be prepared to accept the lining. This is a very critical step. Unless the surface is properly prepared, proper bonding of the lining to the shell will not be achieved. The basic requirement is that the surface be absolutely clean. To ensure proper bonding, all surfaces to be lined should be abrasiveblasted to white metal in accordance with SSPC specification Tp5-63 or NACE specification 1. A white metal surface condition is defined as being one where all rust, scales, paint, and the like have been removed and the surface has a uniform gray–white appearance. Streaks or stains of rust or other contaminants are not allowed. A near-white blast-cleaned finish equal to SSPC SP-10 is allowed on occasion. This is a more economical finish. In any case, it is essential that the finish be as the lining contractor has specified. Some lining contractors will fabricate the vessel as well as prepare the surface. When the total responsibility is placed on the lining contractor, the problem is simplified, and usually, a better quality product will be the result. When a vessel shell is fabricated from a reinforced thermosetting plastic (RTP), several advantages are realized. The RTPs generally have a wider range of corrosion resistance, but relatively low allowable operating temperatures. When a fluoropolymer-type lining is applied to an RTP shell, the temperature to which the backup RTP is exposed, has been reduced in addition to preventing the RTP from becoming exposed to the chemicals in the process system. An upper temperature limit for using RTP dual laminates is 3508F (1778C). The dual-laminate construction lessens the problem of permeation through liners. If there is permeation, it is believed to pass through the RTP structure at a rate equal to or greater than through the fluoropolymer itself, resulting in no potential for collection of permeate at the thermoplastic-to-thermoset interface. If delamination does not occur, permeation is not a problem.

6.2 Considerations in Liner Selection Before a lining material is selected, careful consideration should be given to several broad categories, specifically materials being handled, operating conditions, and conditions external to the vessel.


Sheet Linings

289

The following information must be known about the materials being handled: 1. What are the primary chemicals being handled and at what concentrations? 2. Are there any secondary chemicals, and if so, at what concentration? 3. Are there any trace impurities or chemicals? 4. Are there any solids present, and if so, what are their particle sizes and concentrations? 5. If a vessel, will there be agitation and to what degree? If a pipeline, what are the flow rates (maximum and minimum)? 6. What are the fluid purity requirements? The answers to the above questions will narrow the selection to those materials that are compatible. This next set of questions will narrow the selection further by eliminating materials that do not have the required physical and/or mechanical properties required. 1. What is the normal operating temperature and temperature range? 2. What peak temperatures can be reached during shutdown, startup, process upset, etc.? 3. Will any mixing areas exist where exothermic or heat-of-mixing temperatures can develop? 4. What is the normal operating pressure? 5. What vacuum conditions and range are possible during operation, startup, shutdown, or upset conditions? 6. Will there be temperature cycling? 7. What cleaning methods will be used? Finally, consideration should be given the conditions external to the vessel or pipe. 1. What are the ambient temperature conditions? 2. What is the maximum surface temperature during operation? 3. What are the insulation requirements? 4. What is the nature of the external environment? This can dictate finish requirements and/or affect the selection of the shell material. 5. What are the external heating requirements? 6. Is grounding necessary?


290


With the answers to these questions, an appropriate selection of liner and shell can be made.

6.3 Design Considerations In addition to selecting a lining material that is resistant to the corrodent being handled, there are three other factors to be considered in the design: permeation, absorption, and environmental stress cracking. Permeation and absorption can cause 1. Bond failure and blistering, resulting from the accumulation of fluids at the bond when the substrate is less permeable than the liner or from corrosion/reaction products if the substrate is attacked by the permeant. 2. Failure of the substrate from corrosive attack. 3. Loss of contents through the substrate and liner as a result of the eventual failure of the substrate. In unbonded linings, it is important that the space between the liner and substrate be vented to the atmosphere, not only to allow minute quantities of permeant vapor to escape but also to prevent expansion of entrapped air from collapsing the liner. 6.3.1 Permeation All materials are somewhat permeable to chemical molecules, but plastic materials tend to be an order of magnitude greater in their permeability rates than metals. Polymers can be permeated by gases, vapors, or liquids. Permeation is strictly a physical phenomenon; there is no chemical attack on the polymer. It is a molecular migration either through microvoids in the polymer (if the structure is more or less porous) or between polymer molecules. Permeation is a function of two variables: one relating to diffusion between molecular chains and the other to the solubility of the permeant in the polymer. The driving forces of diffusion are the concentration gradients in liquids and the partial pressure gradient for gases. Solubility is a function of the affinity of the permeant for the polymer. Material passing through cracks and voids is not related to permeation. These are two distinct happenings. They are not related in any way. Permeation is affected by the following factors: 1. Temperature and pressure 2. Permeant concentration 3. Thickness of the polymer


Sheet Linings

291

An increase in temperature will increase the permeation rate because the solubility of the permeant in the polymer will increase, and as the temperature rises, the polymer chain movement is stimulated, permitting more permeants to diffuse among the chain more easily. For many gases, the permeant rates increase linearly with the partial pressure gradient, and the same effect is experienced with concentration gradients of liquids. If the permeant is highly soluble in the polymer, the permeability increase may not be linear. The thickness of the polymer affects the permeation. An increase in thickness will generally decrease permeation by the square of the thickness. However, there are disadvantages to this approach. First, as the lining thickness is increased, thermal stresses on the bond are increased, resulting in bond failure. Temperature changes and large differences in coefficients of thermal expansion are the most common causes of bond failure. The thickness and modulus of elasticity of the lining material are two of the factors that influence these stresses. In addition, as the thickness of the sheet lining material increases, it becomes more difficult to form, and heat may have to be supplied. Also, the thicker sheets are much more difficult to weld. A third factor is cost. As the thickness of the material increases, not only does the material cost more but the labor costs also increase because of the greater difficulty of working with the material. If polymers such as fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF) are being used, the cost may become prohibitive. The density of the polymer in addition to its thickness will also have an effect on the permeation rate. The higher the specific gravity of the sheet, the fewer the voids that will be present through which permeation can take place. A comparison of the specific gravity between two different polymers will not give an indication of the relative permeation rates. However, a comparison between two liners of the same polymer will provide the difference in the relative permeation rates. The liner having the greater density will have the lower permeation rate. Other chemical and physiochemical properties affecting permeation are 1. Ease of condensation of the permeant. Chemicals that readily condense will permeate at higher rates. 2. The higher the intermolecular chain forces (e.g., van der Waal’s hydrogen bonding) of the polymer, the lower the permeation rate. 3. The higher the level of crystallinity in the polymer, the lower the permeation rate. 4. The greater the degrees of crosslinking within the polymer, the lower the permeation rate. 5. Chemical similarity between the polymer and the permeant. When the polymer and permeant both have similar functional groups, the permeant rate will increase. 6. The smaller the molecule of the permeant, the greater the permeation rate.


292


The magnitude of any of the effects will be a function of the combination of polymer and permeant in actual service. 6.3.2 Absorption Polymers have the potential to absorb varying amounts of corrodents that they come into contact with, particularly organic liquids. This can result in swelling, cracking, and penetration to the substrate. Swelling can cause softening of the polymer, introduce high stresses, and precipitate failure of the bond. If the polymer has a high absorption rate, permeation will probably take place. An approximation of the expected permeation and/or absorption of a polymer can be based on the absorption of water. This data is usually available. Table 6.1 provides the water absorption rates for the more common polymers used for linings. The failure because of absorption can best be understood by considering the “steam cycle” test described in the ASTM standards for lined pipe. A section of lined pipe is subjected to thermal and pressure fluctuations. This is repeated for 100 cycles. The steam creates a temperature and pressure gradient through the liner, causing absorption of a small quantity of steam that condenses to water within the inner wall. Upon pressure release, or on reintroduction of steam, the entrapped water can expand to vapor causing an original micropore. The repeated pressure and thermal cycling enlarges the micropores, ultimately producing visible water-filled blisters within the liner. In an actual process, the polymer may absorb process fluids, and repeated temperature or pressure cycling can cause blisters. Eventually, the corrodent may find its way to the substrate. Related effects can occur when process chemicals are absorbed that may later react, decompose, or solidify within the structure of the plastic. Prolonged retention of the chemicals may lead to their decomposition within TABLE 6.1 Water Absorption Rates for Common Polymers Polymer PVC CPVC PP (Homo) PP (Co) EHMW PE ECTFE PVDF PEA ETFE PTFE FEP

Water Absorption 24 h at 738F/238C (%) 0.05 0.03 0.02 0.03 !0.01 !0.1 !0.04 !0.03 0.029 !0.01 !0.01


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293

the polymer. Although unusual, it is possible for absorbed monomers to polymerized. Several steps can be taken to reduce absorption. For example, thermal insulation of the substrate will reduce the temperature gradient across the vessel, thereby, preventing condensation and subsequent expansion of the absorbed fluids. This also reduces the rate and magnitude of temperature changes, keeping blisters to a minimum. The use of operating procedures or devices that limit the ratio of process pressure reductions or temperature increases will provide additional protection. 6.3.3 Environmental Stress Cracking Stress cracks develop when a tough polymer is stressed for an extended period of time under loads that are small relative to the polymer’s yield point. Cracking will occur with little elongation of the material. The higher the molecular weight of the polymer, the less likelihood of environmental stress cracking, other things being equal. Molecular weight is a function of length of individual chains that make up the polymer. Longer chain polymers tend to crystallize less than polymers of lower molecular weight or shorter chains, and they also have a greater load-bearing capacity. Crystallinity is an important factor affecting stress corrosion cracking. The less the crystallization that takes place, the less the likelihood of stress cracking. Unfortunately, the lower the crystallinity, the greater the likelihood of permeation. Resistance to stress cracking can be reduced by the absorption of substances that chemically resemble the polymer and will plasticize it. In addition, the mechanical strength will also be reduced. Halogenated chemicals, particularly those consisting of small molecules containing fluorine or chlorine, are especially likely to be similar to the fluoropolymers and should be tested for their effect. The presence of contaminants in a fluid may act as an accelerator. For example, polypropylene can safely handle sulfuric or hydrochloric acids, but iron or copper contamination in concentrated. sulfuric or hydrochloric acids can result in the stress cracking of polypropylene.

6.4 Causes of Lining Failure Linings, if properly selected, installed, and maintained, and if the vessel has been properly designed, fabricated, and prepared to accept the lining, promise many useful years of service. However, on occasion, there have been lining failures that can be attributed to one or more of the following causes.


294


6.4.1 Liner Selection Selection is the first step. Essential to this step is a careful analysis of the materials to be handled, their concentrations, and operating conditions as outlined in the beginning of this chapter. Consideration must also be given to the physical and mechanical properties of the liner to ensure that it meets the specified operating conditions. If there is any doubt, corrosion testing should be undertaken to guarantee the resistance of the liner material. 6.4.2 Inadequate Surface Preparation Surface preparation is extremely important. All specifications for surface preparation must be followed. If not done properly, poor bonding can result and/or mechanical damage to the liner is possible. 6.4.3 Thermal Stresses If not properly designed for, thermal stresses produced by thermal cycling can eventually result in bond failure. 6.4.4 Permeation Certain lining materials are subject to permeation when in contact with specific corrodents. When the possibility of permeation exists, an alternate lining material should be selected. Permeation can result in debonding resulting from corrosion products or fluids accumulating at the interface between the liner and substrate. In addition, corrosion of the substrate can result leading to leakage problems and eventual failure of the substrate. 6.4.5 Absorption As with permeation, adsorption of the corrodent by the liner material can result in swelling of the liner, cracking, and eventual penetration to the substrate. This can lead to high stresses and debonding. 6.4.6 Welding Flaws It is essential that qualified personnel perform the welding and that only qualified, experienced contractors be used to install linings. A welding flaw is a common cause of lining failure. 6.4.7 Debonding Debonding can also occur as a result of the use of the wrong bonding agent. Care should be taken that the proper bonding agent is employed for the specific lining being used.


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295

6.4.8 Operation Lined vessels should be properly identified when installed with the allowable operating characteristics of the liner posted to avoid damage to the liner during clean-up or repair operations. Most failures from this cause result while vessels are being cleaned or repaired. If live steam is used to clean the vessel, allowable operating temperatures may be exceeded. If the vessel is solvent-cleaned, then chemical attack may occur.

6.5 Elastomeric Linings Elastomers, sometimes referred to as rubbers, have given many years of service in providing protection to steel vessels. Each of these materials can be compounded to improve certain, of its properties. Because of this, it is necessary that a complete specification for a lining using these materials include specific properties that are required for the application. These include resilience, hysteresis, static or dynamic sheer and compression modulus, flex fatigue and cracking, creep resistance to oils and chemicals, permeability, and brittle point, all in the temperature range to be encountered in service. This will permit a competent manufacturer to propose the proper lining material for the application. Elastomeric linings are sheet-applied and bonded to the steel substrate. Choice of bonding material to be used is dependend on the specific elastomer to be installed. Repair of these linings is relatively simple. Many older vessels with numerous repair patches are still satisfactorily operating. The most common elastomers used for lining applications along with their operating temperature range are shown in Table 6.2. Elastomeric materials can fail as the result of chemical action and/or mechanical damage. Chemical deterioration occurs as the result of a chemical reaction between an elastomer and the medium or by the absorption of the medium into the elastomer. This attack results in the swelling of the elastomer and a reduction in its tensile strength. The degree of deterioration is a function of the temperature and the concentration of the corrodent. In general, the higher the temperature and the higher the concentration of the corrodent, the greater will be the chemical attack. Elastomers, unlike metals, absorb varying quantities of the material they are in contact with, especially organic liquids. This can result in swelling, cracking, and penetration to the substrate of an elastomeric lined vessel. Swelling can cause softening of the elastomer, and in a lined vessel, introduce high stresses and failure of the bond. If an elastomeric lining has high absorption, permeation will probably result. Some elastomers, such as the fluorocarbons, are easily permeated but have very little absorption. An approximation of the expected permeation and/or absorption of an elastomer can be based on the absorption of water. This data is usually available.


296


TABLE 6.2 Elastomers Used as Liners Temperature Range 8F

8C

Elastomer

Minimum

Maximum

Minimum

Maximum

Natural rubber, NR Butyl rubber, IIR Chlorobutyl rubber, CIIR Neoprene, CR Hypalon, CSM Urethane rubber, AU EPDM rubber Nitrile rubber, NBR, Buna-N Polyester elastomer, PE Perfluoroelastomers, FPM Fluoroelastomers, FKM

K59 K30 K30 K13 K20 K65 K65 K40 K40 K58 K10

175 300 300 203 250 250 300 250 302 600 400

K50 K34 K34 K25 K30 K54 K54 K40 K40 K50 K18

80 149 149 95 121 121 149 121 150 316 204

6.5.1 Natural Rubber The maximum temperature for continuous use of natural rubber (NR) is 1758F (808C). The degree of curing that NR is subjected to will determine whether it is classified as soft, semihard, or hard. Soft rubber is the form primarily used for lining material, although, some hard linings are produced. Natural rubber provides excellent resistance to most inorganic salt solutions, alkalies, and nonoxidizing acids. Hydrochloric acid will react with soft rubber to form rubber hydrochloride and, therefore, it is not recommended that NR be used in contact with this acid. Strong oxidizing media such as nitric acid, concentrated sulfuric acid, permanganates, dichromates, chlorine dioxide, and sodium hypochlorite will severely attack rubber. Mineral and vegetable oils, gasoline, benzene, toluene, and chlorinated hydrocarbons also affect rubber. Cold water tends to preserve NR. Natural rubber offers good resistance to radiation and alcohols. 6.5.1.1 Soft Natural Rubber Linings These linings have the advantage of: Ease of application, cure, and repair unaffected by mechanical stresses or rapid temperature changes, making it ideal for outdoor tanks. Good chemical resistance within temperature limitation. See Table 6.3. Excellent to superior physical properties. Maximum tensile elongation, abrasion, and tear resistance. Low cost.


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TABLE 6.3 Compatibility of Soft Natural Rubber with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Alum Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum nitrate Aluminum sulfate Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide sat. Ammonium nitrate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzly alcohol Benzyl chloride Borax Boric acid Butyl acetate Butyl alcohol

8F

8C

X X 150 X X X X 140 X 140 140 160 X X 140 140 140 140 140 X X 140 140 140 140 140 140 X 140 X X X 140 140 140 140 140 X X X 140 X X 140 140 X 140

X X 66 X X X X 60 X 60 60 71 X X 60 60 60 60 60 X X 60 60 60 60 60 60 X 60 X X X 60 60 60 60 60 X X X 60 X X 60 60 X 60 (continued)


298


TABLE 6.3 Continued Maximum Temperature Chemical Butyric acid Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Carbon bisulfide Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid, 50% water Chloracetic acid Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15% Citric acid, conc. Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Hydrobromic acid, dil. Hydrobromic acid, 20%

8F

8C

X 140 140 140 140 140 140 X X 140 140 X X X X 140 X X X X X X X X X X X 140 X X X 140 140 X X X X X 140 140 140 X 140 X X 140 140

X 60 60 60 60 60 60 X X 60 60 X X X X 60 X X X X X X X X X X X 60 X X X 60 60 X X X X X 60 60 60 X 60 X X 60 60 (continued)


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299


8F

8C

Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Phenol Phosphoric acid, 50–80% Potassium bromide, 30% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid fuming Sulfurous acid Zinc chloride

140 X 140 X X X X X 140 X X X X 140 X X X X X X 140 140 140 140 140 X X X X 140 140 140 140 X X X X X X X 140

60 X 60 X X X X X 60 X X X X 60 X X X X X X 60 60 60 60 60 X X X X 60 60 60 60 X X X X X X X 60



300


Limitations of these linings include: Not oil or flame resistant Not ozone, sunlight, or weather resistant Temperature limited to 1408F/608C Cannot be used with dilute hydrochloric acid (5–10%) or spent acids Typical applications for soft natural rubber linings include chemical storage tanks to handle 37% phosphoric acid, hydrofluorosilicic acid, alum, chlorides, and sulfates of ammonia, cadmium, iron, phosphorus, and sodium or inorganic salts in general. This material is suitable to line trailer tanks for transporting the above chemicals. Soft natural rubber is also used to line pipes and fittings. 6.5.1.2 Multiply Natural Rubber Linings Multiply natural rubber linings consist of three layers of rubber: soft natural rubber/hard natural rubber/soft natural rubber. The advantages of these linings are: Better permeation resistance than soft natural rubber Heat resistance to 1608T/718C Ease of application, cure, and repair Good flexibility, reducing the danger of cracking in cold weather, rapid temperature changes, or mechanical stresses Moderate cost The limitations of these linings are: Not oil or flame resistant Cannot be used in transport trucks Refer to Table 6.4 for the compatibility of multiply linings with selected corrodents. Applications for multiply linings include those for soft natural rubber linings with the exceptions noted above. 6.5.1.3 Semihard Natural Rubber Linings Semihard natural rubber linings provide: Ease of application, cure, and repair Excellent chemical and permeation resistance. Refer to Table 6.5. Heat resistance to 1808F/828C Moderate cost


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TABLE 6.4 Compatibility of Multiple Ply (Soft/Hard/Soft) Natural Rubber with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Alum Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid

8F

8C

X X X X X X X 140 160 160 160 X X

X X X X X X X 60 71 71 71 X X

160 160 160 160 160 X X 100 100 160

71 71 71 71 71 X X 38 38 71

160 160 160 X 100 X X X 160 160 160 160 160 X X X 160 X X 160 140

71 71 71 X 38 X X X 71 71 71 71 71 X X X 71 X X 71 60 (continued)


302


TABLE 6.4 Continued Maximum Temperature Chemical Butyl acetate Butyl alcohol Butyric acid Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Carbon bisulfide Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid, 50% water Chloracetic acid Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15% Citric acid, conc. Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry

8F

8C

X 160 X 160 160 140 140 160 160 X X 160 160 X X X X 160 X X X X X X X X X X X X X X X 160 160 X X X X X 160 160 160 X 140 X X

X 71 X 71 71 60 60 71 71 X X 71 71 X X X X 71 X X X X X X X X X X X X X X X 71 71 X X X X X 71 71 71 X 60 X X (continued)


Sheet Linings

303


8F

8C

Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Phenol Phosphoric acid, 50–80% Potassium bromide, 30% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Zinc chloride

160 160 160 X 160 X X X X X 160 100 X X X 140 X X X X X X 160 160 160 160 160 X X X X 160 160 160 160 X X X X X X X 160

71 71 71 X 71 X X X X X 71 38 X X X 60 X X X X X X 71 71 71 71 71 X X X X 71 71 71 71 X X X X X X X 71



304


TABLE 6.5 Compatibility of Semihard Natural Rubber with Selected Corrodents Maximum Temperature Chemical Acetamide Acetic acid, glacial Acetic anhydride Acetone Alum Aluminum chloride, aqueous Aluminum fluoride Aluminum nitrate Aluminum sulfate Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium nitrate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl alcohol Aniline Barium carbonate Barium chloride Barium hydroxide Barium sulfate Benzene Benzoic acid Borax Boric acid Butyl acetate Butyl alcohol Butyric acid Calcium bisulfite Calcium carbonate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Chloracetic acid, 50% water Chloracetic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15% Citric acid, conc. Copper carbonate Copper chloride Copper cyanide

8F

8C

X X X X 180 180 X 100 180 180 180 180 180 X X 180 180 180 180 180 X 180 180 180 180 X 180 180 180 100 180 100 180 180 180 180 180 X 100 100 X X 100 100 180 X 180

X X X X 82 82 X 38 82 82 82 82 82 X X 82 82 82 82 82 X 82 82 82 82 X 82 82 82 38 82 38 82 82 82 82 82 X 38 38 X X 38 38 82 X 82 (continued)


Sheet Linings

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TABLE 6.5 Continued Maximum Temperature Chemical Copper sulfate Cupric chloride, 5% Cupric chloride, 50% Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloride Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Phenol Phosphoric acid, 50–80% Potassium bromide, 30% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming

8F

8C

180 X X 180 180 180 100 180 100 180 180 180 180 180 X X 100 100 180 100 100 100 X X X 100 X 180 180 180 180 180 100 100 X X 180 180 180 180 100 X X X X X

82 X X 82 82 82 38 82 38 82 82 82 82 82 X X 38 38 82 38 38 38 X X X 38 X 82 82 82 82 82 38 38 X X 82 82 82 82 38 X X X X X (continued)


306


TABLE 6.5 Continued Maximum Temperature Chemical Sulfurous acid Zinc chloride

8F

8C

150 180

66 82


These linings are limited by their inability to resist oil or flames and the fact that they are subject to damage by cold weather, sudden extreme temperature changes, or mechanical stresses. In addition, they are not abrasion resistant. Applications include chemical process tanks, pumps, fans, pipe, and fittings. 6.5.1.4 Hard Natural Rubber Linings Hard natural rubber linings have the advantage of: Ease of application, cure, and repair Better chemical, heat, and permeation resistance than soft natural rubber. Refer to Table 6.6. Heat resistance to 2008F/938C Moderate cost Limitations of these linings are: Not oil or flame resistant Subject to damage by cold weather, exposure, sudden extreme temperature changes, or mechanical stresses Not abrasion resistant Not to be used in transport vehicles Typical applications include chemical storage tanks, pickling tanks, pipe and fittings, plating tanks, and various accessories as agitators, pumps, etc. 6.5.2 Isoprene Natural rubber is chemically a natural cis-polyisoprene. Isoprene (IR) is a synthetic cis-polyisoprene. The corrosion resistance of IR is the same as that


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TABLE 6.6 Compatibility of Hard Natural Rubber with Selected Corrodents Maximum Temperature Chemical Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acrylonitrile Adipic acid Allyl alcohol Alum Aluminum chloride, aqueous Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl alcohol Aniline Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzoic acid Borax Boric acid Butyl acetate Butyl alcohol Butyric acid Calcium bisulfite

8F

8C

X 200 200 150 100 100 X 90 80 X 200 200 X 200 190 200 200 200 200 200 200 X X X X 150 200 200 200 200 200 X X 200 200 X 200 200 X X 200 200 200 X 160 150 200

X 93 93 66 38 38 X 32 27 X 93 93 X 93 88 93 93 93 93 93 93 X X X X 66 93 93 93 93 93 X X 93 93 X 93 93 X X 93 93 93 X 71 66 93 (continued)


308


TABLE 6.6 Continued Maximum Temperature Chemical Calcium carbonate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Carbon bisulfide Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Chloracetic acid, 50% water Chloracetic acid Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15% Citric acid, conc. Copper carbonate Copper chloride Copper cyanide Copper sulfate Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Lactic acid, 25% Lactic acid, conc.

8F

8C

200 200 200 200 X 200 200 200 X X X X 200 120 120 X 190 X X X X X X 150 150 200 100 200 200 200 200 200 150 200 150 200 200 200 200 200 200 X X X 150 150 150

93 93 93 93 X 93 93 93 X X X X 93 49 49 X 88 X X X X X X 66 66 93 38 93 93 93 93 93 66 93 66 93 93 93 93 93 93 X X X 66 66 66 (continued)


Sheet Linings

309


8F

8C

Magnesium chloride Malic acid Methyl ethyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Phenol Phosphoric acid, 50–80% Potassium bromide, 30% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 70% Sulfurous acid Zinc chloride

200 150 X 200 150 X X X 150 X 200 200 200 200 200 150 150 X X 200 200 200 200 X 200 200

93 66 X 93 66 X X X 66 X 93 93 93 93 93 66 66 X X 93 93 93 93 X 93 93


of NR. The major difference is that isoprene has no odor and, therefore, can be used in the handling of certain food products. 6.5.3 Neoprene The maximum temperature that neoprene (CR) can be used under is 180–2008F (82–938C). Excellent service is experienced in contact with aliphatic compounds(methyl and ethyl alcohols, ethylene glycols, etc.), aliphatic hydrocarbons, and most freon refrigerants. However, the outstanding properties of neoprene is its resistance to attack from solvents, waxes, fats, oils, greases, and many other petroleum-based products. Dilute mineral acids, inorganic salt solutions, and alkalies can also be handled successfully.


310


Chlorinated and aromatic hydrocarbons, organic esters, aromatic hydroxy compounds, and certain ketones have an adverse effect on neoprene and, consequently, only limited serviceability can be expected with them. Highly oxidizing acid and salt solutions also cause surface deterioration and loss of strength. Included in this category are nitric acid and concentrated sulfuric acid. Table 6.7 provides the compatibility of neoprene with selected corrodents. Reference [1] provides a more detailed listing. The advantages of neoprene include its good chemical resistance, heat resistance to 2008F/938C, good oil resistance, better resistance to ozone, sunlight, and weather than natural rubber, its excellent abrasion resistance, and the fact it is unaffected toy cold weather, rapid temperature changes, or mechanical stresses. On the negative side is the fact that it is more expensive than natural rubber and is more difficult to apply. Typical applications include caustic storage and transportation tanks, sulfuric acid pickle tanks, chemical process and storage tanks, and miscelleneous process equipment accessories. 6.5.4 Butyl Rubber The maximum temperature that butyl rubber (IIR) can be exposed to on a continuous basis is 250–3008F (120–1488C). Butyl rubber is very nonpolar. It has exceptional resistance to dilute mineral acids, alkalies, phosphate ester oils, acetone, ethylene, ethylene glycol, and water. Resistance to concentrated acids, except nitric and sulfuric, is good. It is attacked by petroleum oils, gasoline, and most solvents (except oxygenated solvents) but is resistant to swelling by vegetable and animal oils. Refer to Table 6.8 for the compatibility of butyl rubber with selected corrodents. Reference [1] provides a more detailed listing. Butyl rubber linings nave the following advantages: Unaffected by cold water or rapid temperature changes Heat resistant to 2008F/938C Resistant to ozone, sunlight, and aging Possessed of good chemical and gaseous permeation resistance Resistant to water and oxygenated solvents Resistant to sliding abrasion Able to be used for hydrochloric acid Limitations of butyl rubber are: Not flame or oil resistant More costly and difficult to apply than natural rubber


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TABLE 6.7 Compatibility of Neoprene with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide

8F

8C

200 200 160 160 160 X X X X X 140 160 120 X 200

93 93 71 71 71 X X X X X 60 71 49 X 93

150

66

200 180 200

93 82 93

200 140 X 200 150 150 150 200 200 200 200 200 200 150 150 160

93 60 X 93 66 66 66 93 93 93 93 93 93 66 66 71

X 200 X X 140 X 150 150 230

X 93 X X 60 X 66 66 110 (continued)


312



8F

8C

Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol n-Butylamine Butyl phthalate Butyric acid Calcium bisulfite Calcium carbonate Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate, water Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid, 50% water Chloracetic acid Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10%

200 200 X X 100 150 X X 200 150 X X X 140 60 200

93 93 X X 38 66 X X 93 66 X X X 60 16 93

X X 200 200 200 150 230 230 X 150 200 150

X X 93 93 93 66 110 110 X 66 93 66

X 200 200 X X X 150 X X X X X X X X X 140

X 93 93 X X X 66 X X X X X X X X X 60 (continued)


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313

TABLE 6.7 Continued Maximum Temperature Chemical Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70%

8F

8C

100

38

150 150 160

66 66 71



200 X X X X X X X

93 X X X X X X X (continued)


314



8F

8C

Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

X X X

X X X

X X 150 200 160

X X 66 93 71

200 200 230 230 230 X X 200 200 X 150 100 X X X X X 100 X X X 140 160

93 93 110 110 110 X X 93 93 X 66 38 X X X X X 38 X X X 60 71


Applications include linings for hydrochloric acid storage and processing vessels and mixed acid wastes. Butyl rubber is also used to line pipe and fittings. 6.5.5 Chlorosulfonated Polyethylene (Hypalon) The maximum temperature that Hypalon can be exposed to on a continuous basis is 2508F (1218C). Hypalon is highly resistant to attack by hydrocarbon


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TABLE 6.8 Compatibility of Butyl Rubber with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Amyl acetate Amyl alcohol Aniline Antimony trichloride Barium chloride Barium hydroxide Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid

8F

8C

80 150 110 110 X X 100 X X 190 X 200 200 200 200 180 100 100 200 X 190 200 200 200 150 150 190 190 200 190 150 150 X 150 150 150 150 190 190 90 X 90 150 190 X 190 150

27 66 43 43 X X 38 X X 88 X 93 93 93 93 82 38 38 93 X 88 93 93 93 66 66 88 88 93 88 66 66 X 66 66 66 66 88 88 32 X 32 66 88 X 88 66 (continued)


316


TABLE 6.8 Continued Maximum Temperature Chemical Butyl acetate Butyl alcohol Butyric acid Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium sulfate Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid, 50% water Chloracetic acid Chlorine gas, dry Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15% Citric acid, conc. Copper chloride Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Hydrobromic acid, dil. Hydrobromic acid, 20%

8F

8C

X 140 X 120 150 190 190 190 190 X 190 100 190 190 190 X 90 150 150 150 100 X X X X X X X 190 190 150 190 X 150 150 X X 200 175 160 190 175 190 X 125 125

X 60 X 49 66 88 88 88 88 X 88 38 88 88 88 X 32 66 66 66 38 X X X X X X X 88 88 66 88 X 66 66 X X 93 79 71 88 79 88 X 52 52 (continued)


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317


8F

8C

Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Phenol Phosphoric acid, 50–80% Salicylic acid Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene

125 125 125 140 150 150 150 X 125 125 200 X 90 100 80 X 200 150 X X 125 X 150 150 150 80 200 150 150 150 X X 150 150 150 200 150 X X X X X 200 X X

52 52 52 60 66 66 66 X 52 52 93 X 32 38 27 X 93 66 X X 52 X 66 66 66 27 93 66 66 66 X X 66 66 66 93 66 X X X X X 93 X X (continued)


318


TABLE 6.8 Continued Maximum Temperature Chemical Trichloroacetic acid Zinc chloride

8F

8C

X 200

X 93


oils and fuels, even at elevated temperatures. It is also resistant to such oxidizing chemicals as sodium hypochlorite, sodium peroxide, ferric chloride, and sulfuric, chromic, and hydrofluoric acids. Concentrated hydrochloric acid (37%) can be handled below 1588F (708C). Below this temperature, Hypalon can handle all concentrations without adverse effect. Nitric acid up to 60% concentration at room temperature can also be handled without adverse effect. Hypalon is also resistant to salt solutions, alcohols, and both weak and concentrated alkalies. Aliphatic, aromatic, and chlorinated hydrocarbons, aldehydes, and ketones will attack Hypalon. Hypalon is one of the most weather resistant elastomers available. Oxidation takes place at a very low rate. Sunlight and ultraviolet light have little, if any, adverse effect on its physical properties. It is inherently resistant to ozone attack without the need for the addition of special antioxidants or antiozonates to the formulation. Refer to Table 6.9 for the compatibility of Hypalon with selected corrodents. Reference [1] provides a more detailed listing. Hypalon’s advantages include some oil resistance, excellent resistance to ozone, sunlight, weathering, and chemicals as well as resistance to permeation and abrasion. It is unaffected by cold weather or rapid temperature changes. Hypalon is difficult to apply, is more costly than natural rubber, is not resistant to oxygenated solvents, and requires a pressure cure. Applications include linings of tanks and tank cars containing chromic and high concentrations of sulfuric and nitric acids and other oxidizing chemicals. It is also used for pond liners. 6.5.6 Urethane Rubbers The urethane rubbers are produced from a number of polyurethane polymers. Urethane rubbers operate through the range of 50–2128F (10–1008C). Standard compounds exhibit good low temperature impact resistance and low brittle points. At very low temperatures, the material


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TABLE 6.9 Compatibility of Hypalon with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonia carbonate Ammonia gas Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid

8F

8C

60 X 200 200 200 X 200 X X 140 140 200 200 200 200 180 140 90 190 190 190 200 200 200 200 80 140 200 200 60 200 X 140 140 200 200 200 200 200 X X X 200 140 X 200 200

16 X 93 93 93 X 93 X X 60 60 93 93 93 93 82 60 32 88 88 88 93 93 93 93 27 60 93 93 16 93 X 60 60 93 93 93 93 93 X X X 93 60 X 93 93 (continued)


320


TABLE 6.9 Continued Maximum Temperature Chemical Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyric acid Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Chloracetic acid Chlorine gas, dry Chlorine gas, wet Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride

8F

8C

60 60 60 X 60 200 X 200 90 90 200 200 200 200 100 200 200 X 200 200 200 X 200 X X X 90 X X X 150 150

16 16 16 X 16 93 X 93 32 32 93 93 93 93 38 93 93 X 93 93 93 X 93 X X X 32 X X X 66 66

200 200 X 200 200 200 X 200 200 X X X 200 200

93 93 X 93 93 93 X 93 93 X X X 93 93 (continued)


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TABLE 6.9 Continued Maximum Temperature Chemical Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Fluorine gas, dry Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Pottasium bromide, 30% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70%

8F

8C

200 200 200 140 90 100 100 160 140 90 90 90 90 X X 140 80 200 180 X X X 140 100 100 X X X 100 90 X 200 80 200 200 200 200 200 200 200

93 93 93 60 32 38 38 71 60 32 32 32 32 X X 60 27 93 82 X X X 60 38 38 X X X 38 32 X 93 27 93 93 93 93 93 93 93

200 90 200 200 200 160

93 32 93 93 93 71 (continued)


322


TABLE 6.9 Continued Maximum Temperature Chemical Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfurous acid Toluene Zinc chloride

8F

8C

X X X 160 X 200

X X X 71 X 93

The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. Source: From P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.

remains flexible and has good resistance to thermal shock. The standard compositions can be used at temperatures as low as K808F (K188C). Urethane rubbers have little or no resistance to burning. Some slight improvement can be made in this area by special compounding, but the material will still ignite in an actual fire situation. The urethane rubbers are resistant to most mineral and vegetable oils, greases, and fuels, and to aliphatic and chlorinated hydrocarbons. Aromatic hydrocarbons, polar solvents, esters, and ketones will attack urethane. Alcohols will soften and swell the urethane rubbers. These rubbers have limited service in weak acid solutions and cannot be used with concentrated acids. Nor are they resistant to steam or caustic, but they are resistant to the swelling and deteriorating effects of being immersed in water. The urethane rubbers exhibit excellent resistance to ozone attack and have good resistance to weathering. However, extended exposure to ultraviolet light will reduce their physical properties and will cause the rubber to darken. Table 6.10 lists the compatibility of urethane rubbers with selected corrodents, and Table 6.11 lists the compatibility of polyether urethane rubbers with selected corrodents. Urethane is used to line tanks and piping. It is also applied as a coating to prevent seepage of the corrodent into the concrete and attack of the reinforcing steel. Protection from abrasion and corrosion is also supplied. 6.5.7 Polyester Elastomer In general, the fluid resistance of these polyester rubbers increases with increasing hardness. Since these rubbers contain no plasticizers, they are not susceptible to the solvent extraction or heat volatilization of such additives. Many fluids and chemicals will extract plasticizers from elastomers causing a significant increase in stiffness (modulus) and volume shrinkage.


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TABLE 6.10 Compatibility of Urethane Rubbers with Selected Corrodents Maximum Temperature Chemical Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetone Ammonia gas Ammonium chloride, 10% Ammonium chloride, 28% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium hydroxide, 10% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium sulfate, 10–40% Amyl alcohol Aniline Benzene Benzoic acid Bromine water, dil. Bromine water, sat. Butane Butyl acetate Butyl alcohol Calcium chloride, dil. Calcium chloride, sat. Calcium hydroxide, 10% Calcium hydroxide, 20% Calcium hydroxide, 30% Calcium hydroxide, sat. Cane sugar liquors Carbon bisulfide Carbon tetrachloride Carbonic acid Castor oil Cellosolve Chlorine water, sat. Chlorobenzene Chloroform Chromic acid, 10% Chromic acid, 30% Chromic acid, 40% Chromic acid, 50% Citric acid, 5% Citric acid, 10% Citric acid, 15% Citric acid, conc.

8F

8C

X X X X X X

X X X X X X

90 90 90 90 90 90 80

32 32 32 32 32 32 27

X X X X X X 100 X X X X X 90 90 90

X X X X X X 38 X X X X X 32 32 32

X 90 90 X X X X X X X X X X X

X 32 32 X X X X X X X X X X X (continued)


324


TABLE 6.10 Continued Maximum Temperature Chemical Copper sulfate Corn oil Cottonseed oil Cresol Dextrose Dibutyl phthalate Ethers, general Ethyl acetate Ethyl alcohol Ethylene chloride Ethylene glycol Fomaldehyde, dil. Formaldehyde, 37% Formaldehyde, 50% Glycerine Hydrochloric acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 35% Hydrochloric acid, 38% Hydrochloric acid, 50% Isopropyl alcohol Jet fuel, JP 4 Jet fuel, JP 5 Kerosene Lard oil Linseed oil Magnesium hydroxide Mercury Methyl alcohol Methyl ethyl ketone Methyl isobutyl ketone Mineral oil Muriatic acid Nitric acid Oils and fats Phenol Potassium bromide, 30% Potassium chloride, 30% Potassium hydroxide, to 50% Potassium sulfate, 10% Silver nitrate Soaps Sodium carbonate Sodium chloride Sodium hydroxide, to 50% Sodium hypochlorite, all conc. Sulfuric acid, all conc.

8F

8C

90

32

90 X X X X X X

32 X X X X X X

90 X X X 90 X X X X X X X X 90 90 90 90 90 90 X X 90 X X 80 X 90 90 90 90 90 X X 80 90 X X

32 X X X 32 X X X X X X X X 32 32 32 32 32 32 X X 32 X X 27 X 32 32 32 32 32 X X 27 32 X X (continued)


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TABLE 6.10 Continued Maximum Temperature Chemical Toluene Trichloroethylene Trisodium phosphate Turpentine Water, salt Water, sea Whiskey Xylene

8F

8C

X X 90 X X X X X

X X 32 X X X X X


Overall, PE elastomers are resistant to the same class of chemicals and fluids that the polyurethanes are and can be satisfactorily used at higher temperatures in the same fluids. Polyester elastomers have excellent resistance to nonpolar materials such as oils and hydraulic fluids, even at elevated temperatures. At room temperature, PE elastomers are resistant to most polar fluids such as acids, bases, amines, and glycols. Resistance is very poor at temperatures of 1588F/708C or above. These rubbers should not be in applications requiring continuous exposure to polar fluids at elevated temperatures. The compatibility of PE elastomers with selected corrodents is shown in Table 6.12. PE elastomer are used to line tanks, ponds, swimming pools, and drums. 6.5.8 Chlorobutyl Rubber Chlorobutyl rubber (CIIR) is chlorinated isobutylene–isoprene. CIIR exhibits the same general corrosion resistance as natural rubber but can be used at higher temperatures. Unlike butyl rubber, CIIR cannot be used with hydrochloric acid. Refer to Table 6.13 for the compatibility of chlorobutyl rubber with selected corrodents and Reference [1] for additional listings. Chlorobutyl rubber has the following advantages: Heat resistance to 2008F/938C Unaffected by cold weather or rapid temperature changes Good chemical and permeation resistance Good resistance to ozone, sunlight, and weathering Easier to apply than butyl rubber


326


TABLE 6.11 Compatibility of Polyether Urethane Rubbbers with Selected Corrodents Maximum Tempture Chemical Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetone Acetyl chloride Ammonium chloride, 10% Ammonium chloride, 28% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium hydroxide, 10% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium sulfate, 10–40% Amyl alcohol Aniline Benzene Benzoic acid Benzyl alcohol Borax Butane Butyl acetate Butyl alcohol Calcium chloride, dil. Calcium chloride, sat. Calcium hydroxide, 10% Calcium hydroxide, 20% Calcium hydroxide, 30% Calcium hydroxide, sat. Calcium hypochlorite, 5% Carbon bisulfide Carbon tetrachloride Carbonic acid Castor oil Caustic potash Chloroacetic acid Chlorobenzene Chloroform Chromic acid, 10% Chromic acid, 30% Chromic acid, 40% Chromic acid, 50% Citric acid, 5% Citric acid, 10% Citric acid, 15% Cottonseed oil

8F

8C

X X X X X X X 130 130 130 130 110 110 100 120 X X X X X 90 80 X X 130 130 130 130 130 130 130 X X 80 130 130 X X X X X X X 90 90 90 130

X X X X X X X 54 54 54 54 43 43 38 49 X X X X X 32 27 X X 54 54 54 54 54 54 54 X X 27 54 54 X X X X X X X 32 32 32 38 (continued)


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TABLE 6.11 Continued Maximum Tempture Chemical Cresylic acid Cyclohexane Dioxane Diphenyl Ethyl acetate Ethyl benzene Ethyl chloride Ethylene oxide Ferric chloride, 75% Fluorosilicic acid Formic acid Freon F-11 Freon F-12 Glycerine Hydrofluoric acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 35% Hydrochloric acid, 38% Hydrochloric acid, 50% Hydrofluoric acid, 30% Hydrofluoric acid, 40% Hydrofluoric acid, 50% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Isobutyl alcohol Isopropyl acetate Lactic acid, all conc. Methyl ethyl ketone Methyl isobutyl ketone Monochlorobenzene Muriatic acid Nitrobenzene Olive oil Phenol Potassium acetate Potassium chloride, 30% Potassium hydroxide Potassium sulfate, 10% Propane Propyl acetate Propyl alcohol Sodium chloride Sodium hydroxide, 30% Sodium hypochlorite Sodium peroxide Sodium phosphate, acid Sodium phosphate, alk.

8F

8C

X 80 X X X X X X 100 100 X X X 130 X X X X X X X X X X X X X X X X X X 120 X X 130 130 130 X X X 130 140 X X 130 130

X 27 X X X X X X 38 38 X X X 38 X X X X X X X X X X X X X X X X X X 49 X X 54 54 54 X X X 54 60 X X 54 54 (continued)


328


TABLE 6.11 Continued Maximum Tempture Chemical Sodium phosphate, neut. Toluene Trichloroethylene Water, demineralized Water, distilled Water, salt Water, sea Xylene

8F

8C

130 X X 130 130 130 130 X

54 X X 54 54 54 54 X


Limitations of CIIR include its inability to be used with hydrochloric acid or oils. It is more expensive than natural rubber. 6.5.9 Ethylene Propylene Rubber Ethylene Propylene Rubber (EPDM) has exceptional heat resistance, being able to operate at temperatures of 300–3508F/148–1768C, while also finding applications as low as K708F/K568C. As with other elastomeric materials, it can be compounded to improve specific properties. EPDM remains flexible at low temperatures. Standard compounds have brittle points of K908F/K688C or below. EPDM resists attack from oxygenated solvents such as acetone, methyl ethyl ketone, ethyl acetate, weak acids, and alkalies, detergents, phosphate esters, alcohols, and glycols. It exhibits exceptional resistance to hot water and high pressure steam. The elastomer, being hydrocarbon-based, is not resistant to hydrocarbon solvents or oils, chlorinated hydrocarbons, or turpentine. Ethylene propylene terpolymer rubbers are, in general, resistant to most of the same corrodents as EPDM but do not have as broad a resistance to mineral acids and some organics. Ethylene propylene rubbers are particularly resistant to sun, weather, and ozone attack. Ozone resistance is inherent in the polymer, and for all practical purposes, it can be considered immune to ozone attack. The compatibility of EPDM rubber with selected corrodents will be found in Table 6.14 with additional listings in Reference [1].


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TABLE 6.12 Compatibility of Polyester Elastomers with Selected Corrodents Maximum Temperature Chemical

8F

8C

Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic acid, vapor Ammonium chloride, 10% Ammonium chloride, 28% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium sulfate, 10–40% Amyl acetate Aniline Beer Benzene Borax Boric acid Bromine, liquid Butane Butyl acetate Calcium chloride, dil. Calcium chloride, sat. Calcium hydroxide, 10% Calcium hydroxide, 20% Calcium hydroxide, 30% Calcium hydroxide, sat. Calcium hypochlorite, 5% Carbon bisulfide Carbon tetrachloride Castor oil Chlorine gas, dry Chlorine gas, wet Chlorobenzene Chloroform Chlorosulfonic acid Citric acid, 5% Citric acid, 10% Citric acid, 15% Citric acid, conc. Copper sulfate Cottonseed oil Cupric chloride, to 50% Cyclohexane Dibutyl phthalate Dioctyl phthalate Ethyl acetate Ethyl alcohol Ethylene chloride

80 80 80 100 90 90 90 90 90 80 80 X 80 80 80 80 X 80 80 80 80 80 80 80 80 80 80 X 80 X X X X X 80 80 80 80 80 80 80 80 80 80 80 80 X

27 27 27 38 32 32 32 32 32 27 27 X 27 27 27 27 X 27 27 27 27 27 27 27 27 27 27 X 27 X X X X X 27 27 27 27 27 27 27 27 27 27 27 27 X (continued)


330



8F

8C

Ethylene glycol Formaldehyde, dil. Formaldehyde, 37% Formic acid, 10–85% Glycerine Hydrochloric acid, dil. Hydrochloric acid, 20% Hydrochloric acid, 35% Hydrochloric acid, 38% Hydrochloric acid, 50% Hydrofluoric acid, dil. Hydrofluoric acid, 30% Hydrofluoric acid, 40% Hydrofluoric acid, 50% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hydrogen Hydrogen sulfide, dry Lactic acid Methyl ethyl ketone Methylene chloride Mineral oil Muriatic acid Nitric acid Nitrobenzene Ozone Phenol Potassium dichromate, 30% Potassium hydroxide Pyridine Soap solutions Sodium chloride Sodium hydroxide, all conc. Stannous chloride, 15% Stearic acid Sulfuric acid, all conc. Toluene Water, demineralized Water, distilled Water, salt Water, sea Xylene Zinc chloride

80 80 80 80 80 80 X X X X X X X X X X 80 80 80 80 X 80 X X X 80 X 80 80 80 80 80 80 80 80 X 80 160 160 160 160 80 80

27 27 27 27 27 27 X X X X X X X X X X 27 27 27 27 X 27 X X X 27 X 27 27 27 27 27 27 27 27 X 27 71 71 71 71 27 27



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TABLE 6.13 Compatibility of Cholorobutyl Rubber with Selected Corrodents Maximum Temperature Chemical

8F

8C

Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Alum Aluminum chloride, aqueous Aluminum nitrate Aluminum sulfate Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium nitrate Ammonium phosphate Ammonium sulfate, 10–40% Amyl alcohol Aniline Antimony trichloride Barium chloride Benzoic acid Boric acid Calcium chloride Calcium nitrate Calcium sulfate Carbon monoxide Carbonic acid Chloracetic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15% Copper chloride Copper cyanide Copper sulfate Cupric chloride, 5% Cupric chloride, 50% Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38%

150 150 150 X X 100 200 200 190 200 200 200 200 200 200 150 150 150 150 150 150 150 150 160 160 160 100 150 100 X X 90 150 160 160 150 150 200 175 100 160 175 125 125 125 X X

60 60 60 X X 38 93 93 88 93 93 93 93 93 93 66 66 66 66 66 66 66 66 71 71 71 38 66 38 X X 32 66 71 71 66 66 93 79 38 71 79 52 52 52 X X (continued)


332


TABLE 6.13 Continued Maximum Temperature Chemical Hydrofluoric acid, 70% Hydrofluoric acid, 100% Lactic acid, 25% Lactic acid, conc. Magnesium chloride Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Phenol Phosphoric acid, 50–80% Sodium chloride Sodium hydroxide, 10% Sodium sulfide, to 50% Sulfuric acid, 10% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Zinc chloride

8F

8C

X X 125 125 200 200 150 X X 125 150 150 200 150 150 200 X X X X X 200 200

X X 52 52 93 93 66 X X 52 66 66 93 66 66 93 X X X X X 93 93


The advantages of EPDM as a lining material are many: It has a high heat resistance. It is unaffected by cold or rapid temperature changes. It has excellent resistance to sunlight, ozone, and weather. It has good abrasion and chemical resistance. On the negative side is the fact that it is neither oil nor flame resistant, and it is difficult to apply. EPDM has been used to line sodium hypochlorite storage and make-up tanks and has been used as a lining for other bleach solutions. Pumps have also been lined with EPDM. The compatibility of ethylene propylene terpolymer (EPT) rubbers with selected corrodents can be found in Reference [1].


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TABLE 6.14 Compatibility of EDPM Rubber with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10%

8F

8C

200 200 140 140 140 140 X 200 X 140 200 200 X 200 190 200 200 190 200 200 200 200 200 200 200 200 100 100 200 200 200 200 200 200 200 X 140 200 X 200 200 200 200 140 150 X X

93 93 60 60 60 60 X 93 X 60 93 93 X 93 88 93 93 88 93 93 93 93 93 93 93 93 38 38 93 93 93 93 93 93 93 X 60 93 X 93 93 93 93 60 66 X X (continued)


334


TABLE 6.14 Continued Maximum Temperature Chemical Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyric acid Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 50% Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5%

8F

8C

X X X 200 190 X X X X 140 200 140 X 200 140 200 200 200 200 200 200 200 X 200 200 200 X 200 X 200 160 X X X X X X X 200 200 100 200 200 200 200 X 200

X X X 93 88 X X X X 60 93 60 X 93 60 93 93 93 93 93 93 93 X 93 93 93 X 93 X 93 71 X X X X X X X 93 93 38 93 93 93 93 X 93 (continued)


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TABLE 6.14 Continued Maximum Temperature Chemical Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Oleum Perchloric acid, 10% Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc.

8F

8C

200 X X X 200 200 200 200 200 200 60 90 140 140 100 90 200 60 X X 200 140 X 140

93 X X X 93 93 93 93 93 93 16 32 60 60 38 32 93 16 X X 93 60 X 60

200 X X 80 60 60 60 X X X 140 140 200 200 200 200 140 200 180 180 200 200

93 X X 27 16 16 16 X X X 60 60 93 93 93 60 93 82 82 93 93 (continued)


336


TABLE 6.14 Continued Maximum Temperature Chemical Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Toluene Trichloroacetic acid White liquor Zinc chloride

8F

8C

200 200 200 150 150 140 X X X X X 80 200 200

93 93 93 66 66 60 X X X X X 27 93 93


6.5.10 Nitrile Rubber (NBR, Buna-N) Nitrile rubber is a copolymer of butadiene and acrylonitrile. The main advantages of the nitrile rubbers are their low cost, good oil and abrasion resistance, and good low temperature and swell characteristics. The nitrile rubbers exhibit good resistance to solvents, oil, water, and hydraulic fluids. A very slight swelling occurs in the presence of aliphatic hydrocarbons, fatty acids, alcohols, and glycols. The deterioration of physical properties as a result of this swelling is small, making NBR suitable for gas and oil resistant applications. The use of highly polar solvents such as acetone and methyl ethyl ketone, chlorinated hydrocarbons, ethers and esters should be avoided because these materials will attack the nitrile rubbers. Table 6.15 shows the compatibility of the nitrile rubbers with selected corrodents. Nitrile rubbers are unaffected by cold weather or rapid temperature change and provide excellent resistance to aliphatic hydrocarbons. They also have good abrasion resistance. However, this material is more costly than natural rubber and is more difficult to apply. Buna-N is used to line tanks and piping. 6.5.11 Fluoroelastomers Fluoroelastomers (FKM) are fluorine containing hydrocarbon polymers with a saturated structure obtained by polymerizing fluorinated monomers such


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TABLE 6.15 Compatibility of Nitrile Rubber with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aqueous Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonia gas Ammonium carbonate Ammonium nitrate Ammonium phosphate Amyl alcohol Aniline Barium chloride Benzene Benzoic acid Boric acid Calcium hypochlorite Carbonic acid Ethylene glycol Ferric chloride Ferric nitrate, 10–50% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Phenol Phosphoric acid, 50–80% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hypochlorite, 20% Sodium hypochlorite, conc. Stannic chloride Sulfuric acid, 10%

8F

8C

X 180 X X X X X X X X X 180 180 X 150 150 180 190 200 190 X 150 150 150 X 125 150 150 150 X 100 100 150 150 X X X X X X 150 125 200 150 X X 150 150

X 82 X X X X X X X X X 82 82 X 66 66 82 88 93 88 X 66 66 66 X 52 66 66 66 X 38 38 66 66 X X X X X X 66 52 93 66 X X 66 66 (continued)


338


TABLE 6.15 Continued Maximum Temperature Chemical Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Zinc chloride

8F

8C

150 X X X X X 150

66 X X X X X 66


as vinylidene fluoride, hexafluoroprene, and tetrafluoroethylene. The result is a high-performance rubber with exceptional resistance to oils and chemicals at elevated temperatures. As with other rubbers, fluoropolymers are capable of being compounded with various additives to enhance specific properties for particular applications. Fluoropolymers are manufactured under various tradenames by different manufacturers. Three typical materials are listed below: Trade Name

Manufacturer

Viton Technoflon Fluorel

DuPont Ausimont 3M

The temperature resistance of the fluoroelastomers is exceptionally good over a wide temperature range. At high temperatures, their mechanical properties are retained better than those of any other elastomer. Compounds remain usefully elastic indefinitely when exposed to aging up to 4008F/2048C. Continuous service limits are generally considered to be as follows: 3000 h at 4508F/2328C 1000 h at 5008F/2608C 240 h at 5508F/2688C 48 h at 6008F/3138C


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These compounds are suitable for continuous use at 4008F/2058C depending upon the corrodent. On the low temperature side, these rubbers are generally serviceable in dynamic applications down to K108F/K238C. Flexibility at low temperatures is a function of the material thickness. The thinner the cross section, the less stiff the material is at every temperature. The brittle point at a thickness of 0.075 in. (1.9 mm) is in the neighborhood of K508F/K458C. Being halogen-containing polymers, these elastomers are more resistant to burning than exclusively hydrocarbon rubbers. Normally compounded material will burn when directly exposed to flame, but it will stop burning when the flame is removed. However, it must be remembered that under an actual fire condition, the fluoroelastomers will burn. During combustion, fluorinated products such as hydrochloric acid can be given off. Special compounding can improve the flame resistance. One such formulation has been developed for the space program that will ignite under conditions of the NASA test that specifies 100% oxygen at 6.2 psi absolute. Fluoroelastomers have been approved by the U.S. Food and Drug Administration for use in repeated contact with food products. The fluoropolymers provide excellent resistance to oils, fuels, lubricants, most mineral acids, many aliphatic and aromatic hydrocarbons (carbon tetrachloride, benzene, toluene, and xylene) that act as solvents for other rubbers, gasoline, naphtha, chlorinated solvents, and pesticides. Special formulations can be produced to obtain resistance to hot mineral acids. These elastomers are not suitable for use with low molecular weight esters and ethers, certain amines, or hot anhydrous hydra-fluoric or chlorosulfonic acids. Table 6.16 provides the compatibility of fluoroelastomers with selected corrodents. Reference [1] provides additional information. The main applications of the fluoroelastomers are in those applications requiring resistance to high operating temperatures together with high chemical resistance to aggressive media and to those characterized by severe operating conditions that no other elastomer can withstand. Linings and coatings are such applications. Their chemical stability solves the problem of chemical corrosion by making it possible to use them for such purposes as: A protective lining for power station stacks operated with high sulfur fuels Tank linings for the chemical industry The advantages of the fluoroelastomers are in their high degree of resistance to aggressive media. Their cost is less than the perfluoroelastomers but greater than other elastomeric materials used for the lining of vessels.


340


TABLE 6.16 Compatibility of Fluoroelastomers with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate

8F

8C

X 210 190 180 180 X X X 400 X X 190 190 100 190 180 400 400 190 400 X 390 X 140 190 400 300 300 140 140 190 190 X 140 180 180 X X 200 190 230 190 190 250 400 400 400

X 199 88 82 82 X X X 204 X X 82 88 38 88 82 204 204 88 204 X 199 X 60 88 204 149 149 60 60 88 88 X 60 82 82 X X 93 88 110 88 88 121 204 204 204 (continued)


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8F

8C

Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry, 25% Bromine gas, moist, 25% Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyl phthalate n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium sulfate Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15%

400 X 400 190 400 400 400 190 400 180 180 350 400 X 400 80 X 120 400 400 190 190 300 300 400 400 400 200 400 80 X 400 400 350 400 X X X 190 190 190 400 400 X 350 350 300

204 X 204 88 204 204 204 88 204 82 82 177 204 X 204 27 X 49 204 204 88 88 149 149 204 204 204 93 204 27 X 204 204 177 204 X X X 88 88 88 204 204 X 177 177 149 (continued)


342


TABLE 6.16 Continued Maximum Temperature Chemical Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum

8F

8C

400 X 190 400 400 400 X 180 180 400 400 190 400 400 400 400 180 210 X X 400 400 400 350 350 400 210 350 X 400 190 X 300 400 390 390 180 190 X X 350 400 400 190 190 90 190

204 X 88 204 204 204 X 82 82 204 204 88 204 204 204 204 82 99 X X 204 204 204 177 177 204 99 177 X 204 88 X 149 204 199 199 82 88 X X 149 204 204 88 88 32 88 (continued)


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8F

8C

Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, turning Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

400 400 210 300 400 190 300 190 400 X X X 400 400 190 400 400 350 350 350 350 350 180 200 400 X 400 190 190 400

204 204 99 149 204 88 149 88 204 X X X 204 204 88 204 204 149 149 149 149 149 82 93 204 X 204 88 88 204


6.6 Thermoplastic Linings Thermoplastic linings are used more extensively than any other type of linings. The most common thermoplasts used are Polyvinyl chloride (PVC) Chlorinated polyvinyl chloride (CPVC) Polyvinylidene fluoride (PVDF)


344


Polypropylene (PP) Polyethylene (PE) Tetrafluoroethylene (PTFE) Fluorinated ethylene propylene (FEP) Perfluoralkoxy (PEA) Ethylene-tetrafluoroethylene (ETFE) Ethylene-chlorotrifluorethylene (ECTFE) These materials are capable of providing a wide range of corrosion resistance. Table 6.17 lists the general area of corrosion resistance for each of the thermoplasts, but it is only a general guide. The resistance of a lining material to a specific corrodent should be checked. These materials are used to line vessels as well as pipes and fittings. When vessels are lined, the linings, with the exception of plasticized PVC, are fabricated from sheet stock that must be cut, shaped, and joined. Joining is usually accomplished by hot-gas welding. Several problems exist when a thermoplastic lining is bonded to a metal shell, primarily the large differences in the coefficient of thermal expansion and the difficulty of adhesion. If the vessel is to be used under ambient temperature, such as a storage vessel, the problems of thermal expansion differences are eliminated. However, the problem of adhesion is still present. Because of this, many linings are installed as loose linings in the vessel. Techniques have been developed to overcome the problem of adhesion that make use of an intermediate bond. One approach is to heat the thermoplastic sheet then impress it into one surface a fiber cloth or nonwoven web. This provides half of the bond. Bonding to the metal surface is accomplished by the use of an epoxy adhesive that will bond to both the fiber and the metal. Welding techniques for joining the thermoplastic sheets are very critical. Each weld must be continuous, leak-tight, and mechanically strong. It is TABLE 6.17 General Corrosion Resistance of Thermoplastic Lining Materials Material

Strong Acids

Strong Bases

Chlorinated Solvents

Esters and Ketones

Strong Oxidants

PVC (type 1) CPVC PVDF PP PE PTFE FEP PFA ETFE ECTFE

F F E G F E E E E E

F F P E G E E E E E

P F E P P E E E E E

P P P F P E E E E E

P P E P E E E E E E

E, excellent; G, good; F, fair, P, poor.


Sheet Linings

345

important that only qualified welders be used for this operation. Poor welding is a common cause of lining failure. 6.6.1 Polyvinyl Chloride The maximum allowable temperature for continuous operation of type 1 polyvinyl chloride (PVC) is 1408F (608C). Plasticized PVC can be bonded directly to a metal substrate. Unplasticized PVC cannot be bonded directly. It is bonded to a plasticized material forming a dual laminate that is then bonded to a metal substrate. Plasticized PVC does not have the same range of corrosion resistance as the unplasticized PVC (type 1), Unplasticized PVC is resistant to attack by most acids and strong alkalies as well as gasoline, kerosene, aliphatic alcohols, and hydrocarbons. It is subject to attack by aromatics, chlorinated organic com-pounds, and lacquer solvents. In addition to handling highly corrosive and abrasive chemicals, these linings have found many applications in marine environments. Table 6.18 lists the compatibility of type 1 PVC with selected corrodents and Table 6.19 does the same for type 2 PVC. Additional data can be found in Reference [1]. 6.6.2 Chlorinated Polyvinyl Chloride Chlorinated polyvinyl chloride (CPVC) can be continuously operated at a maximum temperature of 2008F (938C). CPVC is very similar in properties to PVC except that it has a higher allowable operating temperature and a somewhat better resistance to chlorinated solvents. It is extremely difficult to hot-weld the joints in a sheet lining. This factor should be considered when selecting this material. CPVC is resistant to most acids, alkalies, salts, halogens, and many corrosive waters. In general, it should not be used to handle most polar organic materials, including chlorinated or aromatic hydrocarbons, esters, and ketones. Table 6.20 lists the compatibility of CPVC with selected corrodents. Reference [1] provides a more detailed listing. 6.6.3 Polyvinylidene Fluoride Polyvinylidene fluoride (PVDF) may be continuously operated at a maximum temperature of 2758F (1358C). It is one of the most popular lining materials because of its range of corrosion resistance and high allowable operating temperature. Unless a dual laminate is used, linings of PVDF will be loose. PVDF is resistant to most acids, bases, and organic solvents. It also has the ability to handle wet or dry chlorine, bromine, and other halogens. It is not resistant to strong alkalies, fuming acids, polar solvents, amines, ketones, and esters. When used with strong alkalies, it stress-cracks.


346


TABLE 6.18 Compatibility of Type 1 PVC with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride

8F

8C

X X 140 140 140 130 X X X X X 140 90 X 140 100 140 140 140 140 140 140 140 140 90 140 140 140 140 140 140 140 140 140 140 140 140 140 120 X 140 X X 140 X 140 140

X X 60 60 60 54 X X X X X 60 32 X 60 38 60 60 60 60 60 60 60 60 32 60 60 60 60 60 60 60 60 60 60 60 60 60 49 X 60 X X 60 X 60 60 (continued)


Sheet Linings

347


8F

8C

Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyl phthalate n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform

140 140 140 X X 140 140 X 60 140 140 X X X 140 X X 80 X 60 140 140 140 140 140 140 140 140 140 140 140 120 X 140 140 X 140 X 140 X 140 140 140 X X X X

60 60 60 X X 60 60 X 16 60 60 X X X 60 X X 27 X 16 60 60 60 60 60 60 60 60 60 60 60 49 X 60 60 X 60 X 60 X 60 60 60 X X X X (continued)


348


TABLE 6.18 Continued Maximum Temperature Chemical Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hvdrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 100% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid

8F

8C

60 140 140 120 140 140 80 140 140 140 140 130 140 140 80 X 120 X 140 140 140 140 140 140 X X 140 140 140 140 140 140 X 120 68 140 100 X 140 80 140 140 90 X X X 140

16 60 60 49 60 60 27 60 60 60 60 54 60 60 27 X 49 X 60 60 60 60 60 60 X X 60 60 60 60 60 60 X 49 20 60 38 X 60 27 60 60 32 X X X 60 (continued)


Sheet Linings

349


8F

8C

Nitric acid, 5% Nitric acid 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Pherchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

140 140 140 X 60 X 140 60 X 140 X 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 X X X 140 X X 90 140 140

60 60 60 X 16 X 60 16 X 60 X 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 X X X 60 X X 32 60 60



350


TABLE 6.19 Compatibility of Type 2 PVC with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate

8F

8C

X X 100 90 X X X X X X X 140 90 X 140 100 140 140 140 140 140 140 140 90 140 140 140 140 90 90 140 140 140 140 140 140 140 X X X X 140 X 140 140 140 140

X X 38 32 X X X X X X X 60 32 X 60 38 60 60 60 60 60 60 60 32 60 60 60 60 32 32 60 60 60 60 60 60 60 X X X X 60 X 60 60 60 60 (continued)


Sheet Linings

351


8F

8C

Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butric acid Butyl acetate Butyl alcohol n-Butylamine Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15% Citric acid, conc. Copper carbonate Copper chloride

140 X X 140 140 X 140 140 X X X 60 X X X X 140 140 140 140 140 140 140 140 140 140 140 140 140 X 140 X 140 X 105 140 X X X X 60 140 X 140 140 140 140

60 X X 60 60 X 60 60 X X X 16 X X X X 60 60 60 60 60 60 60 60 60 60 60 60 60 X 60 X 60 X 40 60 X X X X 16 60 X 60 60 60 60 (continued)


352


TABLE 6.19 Continued Maximum Temperature Chemical Copper cyanide Copper sulfate Cresol Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hypochlorous acid Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride

8F

8C

140 140 X X 120 X 140 140 140 140 140 X X 140 140 140 140 140 140 120 68 140 X 140 80 140 140 X X X 140 100 140 70 X 60 X 60 60 X 140 X 140 X 105 140 140

60 60 X X 49 X 60 60 60 60 60 X X 60 60 60 60 60 60 49 20 60 X 60 27 60 60 X X X 60 38 60 23 X 16 X 16 16 X 60 X 60 X 40 60 60 (continued)


Sheet Linings

353


8F

8C

Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

140 140 140 140 140 140 140 140 140 140 140 X X X X 140 X X X 140 140

60 60 60 60 60 60 60 60 60 60 60 X X X X 60 X X X 60 60


PVDF is manufactured under various trade names: Trade Name Kynar Solef Hylar

Manufacturer Elf Atochem Solvay Ausimont USA

Refer to Table 6.21 for the compatibility of PVDF with selected corrodents. Reference [1] provides additional listings. 6.6.4 Polypropylene The maximum allowable temperature that polypropylene (PP) can be continuously operated under is 1808F (828C). PP must be attached to


354


TABLE 6.20 Compatibility of CPVC with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol, 96% Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas, dry Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide

8F

8C

X 90 X X X X X X X X 200 200 X 200 100 200 180 200 200 200 200 200 200 140 200 180 180 200 200 200 X X 200 200 200 200 200 160 X 130 X X 200 80 200 180 180

X 32 X X X X X X X X 93 93 X 93 33 93 82 93 93 93 93 93 93 60 93 82 82 93 93 93 X X 93 93 93 93 93 71 X 54 X X 93 27 93 82 82 (continued)


Sheet Linings

355


8F

8C

Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10%

180 180 X X 180 200 X X 200 210 X X X 150 X 140 X 140 180 210 210 180 180 170 210 200 180 180 180 180 X 210 160 X 210 X 180 180 X 100 140 X X X X X 210

82 82 X X 82 93 X X 93 99 X X X 66 X 60 X 60 82 99 99 82 82 77 99 93 82 82 82 82 X 99 71 X 99 X 82 82 X 38 60 X X X X X 99 (continued)


356


TABLE 6.20 Continued Maximum Temperature Chemical Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid, 20% Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70%

8F

8C

210 180 180 180 80 180 210 180 210 X 180 180 X X 100 X 210 210 180 180 210 180 X 80 130 180 190 180 170 80 X 90 X 180 X 180 100 230 180 180 X X X 170 180 160 180

99 82 82 82 27 82 99 82 99 X 82 82 X X 38 X 99 99 82 82 99 82 X 27 54 82 88 82 77 27 X 32 X 82 X 82 38 110 82 82 X X X 77 82 71 82 (continued)


Sheet Linings

357


8F

8C

Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid, 20% White liquor Zinc chloride

X 80 X 180 180 140 180 X 180 X 170 210 210 190 180 190 190 180 180 180 180 180 180 200 X X X X 180 X X 140 180 180

X 27 X 82 82 60 82 X 82 X 77 99 99 88 82 88 88 82 82 82 82 82 82 93 X X X X 82 X X 60 82 82

The chemicals listed are in the pure state or in saturated solution unless otherwise indicated. Compatibilty is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. Source: From P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.

a backing sheet in order to be secured as a lining. If a backing sheet is not used, the lining will be loose. PP is resistant to sulfur-bearing compounds, caustics, solvents, acids, and other organic chemicals. It is not resistant to oxidizing-type acids, detergents, low-boiling hydrocarbons, alcohols, aromatics, and some chlorinated organic materials.


358


TABLE 6.21 Compatibility of PVDF with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride

8F

8C

150 90 300 300 190 190 100 X 120 150 130 280 200 200 180 250 300 270 300 260 300 290 300 270 250 280 280 280 280 280 280 280 280 280 280 280 280 280 280 190 280 280 200 150 130 280 280

66 32 149 149 88 88 38 X 49 66 54 138 93 93 82 121 149 132 149 127 149 143 149 132 121 138 138 138 138 138 138 138 138 138 138 138 138 138 138 88 138 138 93 66 54 138 138 (continued)


Sheet Linings

359


8F

8C

Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyl phthalate n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet, 10% Chlorine, liquid Chlorobenzene Chloroform

280 280 280 120 150 100 250 280 280 280 280 210 210 140 280 140 280 80 X 230 280 280 280 280 280 270 280 280 280 250 280 220 80 280 280 80 280 280 280 280 200 210 210 210 210 220 250

138 138 138 49 66 38 121 138 138 138 138 99 99 60 138 60 138 27 X 110 138 138 138 138 138 132 138 138 138 121 138 104 27 138 138 27 138 138 138 138 93 99 99 99 S9 104 121 (continued)


360


TABLE 6.21 Continued Maximum Temperature Chemical Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferrous chloride Ferrous nitrate Ferrous nitrate, 10–50% Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid

8F

8C

110 220 250 110 250 250 250 250 280 280 280 210 270 270 250 210 120 280 280 280 280 280 280 280 80 80 260 280 280 280 280 280 260 200 200 280 250 110 130 110 280 250 280 X X 110 280

43 104 121 43 121 121 121 121 138 138 138 99 132 132 121 99 49 138 138 138 138 138 138 138 27 27 127 138 138 138 138 138 127 93 93 138 121 43 54 43 138 121 138 X X 43 138 (continued)


Sheet Linings

361


8F

8C

Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

200 180 120 150 210 X 210 120 200 220 80 280 220 250 280 280 230 220 150 280 280 280 280 280 250 220 220 210 140 X X 220 X X 130 80 260

93 82 49 66 99 X 99 49 93 104 27 138 104 121 138 138 110 104 66 138 138 138 138 138 121 104 104 99 60 X X 104 X X 54 27 127


Polypropylene has FDA approval for handling of food products. It should not be used with oxidizing type acids, detergents, low boiling hydrocarbons, alcohols, aromatics, and some chlorinated organic materials.


362


Polypropylene may be subject to environmental stress cracking. The occurrence is difficult to predict. It is dependent upon the process chemistry, operating conditions, and quality of fabrication. In Table 6.22 that gives the compatibility of PP with selected corrodents, certain chemical/liner ratings are identified by an “e” indicating that the liner in contact with that specific chemical may be susceptible to ESC. Reference [1] provides a more comprehensive listing. 6.6.5 Polyethylene The maximum allowable temperature, at continuous contact that polyethylene (PE) can be used is 1208F (498C). PE is the least expensive of all the plastic materials. PE has a wide range of corrosion resistance ranging from potable water to corrosive wastes. It exhibits excellent resistance to strong oxidizing chemicals, alkalies, acids, and salt solutions. Physical and mechanical properties differ by density and molecular weight. The three main classifications of density are low, medium, and high. These specific gravity ranges are 0.91–0.925, 0.925–0.940, and 0.940–0.965. These grades are sometimes referred to as types 1, 11, and 111. Industry practice breaks the molecular weight of polyethylenes into four distinct classifications: Medium molecular weight: less than 100,000 High molecular weight: 110,000–250,000 Extra high molecular weight: 250,000–1,500,000 Ultra high molecular weight: 1,500,000 and higher Usually, the ultra high molecular weight material has a molecular weight of at least 3.1 million. The two varieties of polyethylene used, for corrosive applications are EHMW and UHMW. The key properties of these two varieties are: Good abrasion resistance Excellent impact resistance Light weight Easily heat fused High tensile strength Low moisture absorption Nontoxic Nonstaining Corrosion resistant


Sheet Linings

363

TABLE 6.22 Compatibility of PP with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitryle Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride

8F

8C

120 110 220 200 200 190 100 220 X X 90 100 140 140 220 100 200 220 200 200 200 220

49 43 104 93 93 88 38 104 X X 32 38 60 60 104 38 93 104 93 93 93 104

150 200 220 180 180 200 210 200 200 200 200 220 200 200 220 220 X 200 X 180 180 X 200 220

66 93 104 82 82 93 99 93 93 93 93 104 93 93 104 104 X 93 X 82 82 X 93 104 (continued)


364



8F

8C

Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyl phthalate n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform

200 200 200 80 140 180 190 140 80 210 220 X X X X X 200 180 90 180 210 210 210 220 220 200 220 210 210 220 220 140 X 220 140 X 220 X 220 200 180 80 X X X X X

93 93 93 27 60 82 88 60 27 99 104 X X X X X 93 82 32 82 99 99 99 104 104 93 104 99 99 104 104 60 X 104 60 X 104 X 104 93 82 27 X X X X X (continued)


Sheet Linings

365

TABLE 6.22 Continued Maximum Temperature Chemical Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroethane (ethylene dichloride) Dictiloroacetic acid Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid

8F

8C

X 140 e150 140 220 220 80 200 200 200 200 X 140 140 X 150 80 100 210 e210 210 210 e210 210 X X 230 200 190 220 200 150 180 200 200 140 X 110 150 150 210 130 120 X X 80 200

X 60 66 60 104 104 27 93 93 93 93 X 60 60 X 66 27 38 99 99 99 99 99 99 X X 110 93 88 104 93 66 82 93 93 60 X 43 66 66 99 54 49 X X 27 93 (continued)


366



8F

8C

Nitric acid anhydrous Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

X 140 140 X X X 140 X 180 210 140 210 130 170 220 200 220 220 140 120 110 190 150 200 200 200 180 180 120 X X 180 100 X 150 220 200

X 60 60 X X X 60 X 82 99 60 99 54 77 104 93 104 104 60 49 43 88 66 93 93 93 82 82 49 X X 82 38 X 66 104 93



Sheet Linings

367

Polyethylene exhibits a wide range of corrosion resistance—ranging from potable water to corrosive wastes. It is resistant to most mineral acids, including sulfuric up to 70% concentration, inorganic salts including chlorides, alkalies, and many organic acids. It is not resistant to bromine, aromatics, or chlorinated hydrocarbons. Refer to Table 6.23 for the compatibility of EHMWPE with selected corrodents and Table 6.24 for HMWPE’s compatibility. Reference [1] provides a more comprehensive listing. 6.6.6 Tetrafluoroethylene Tetrafluoroethylene (PTFE) can be used continuously at 5008F (2608C). It cannot be bonded directly to metal substrates, but it can be bonded with a laminated fiberglass sheet as a backing. The material tends to creep under stress at elevated temperatures. When the vessel is designed, provisions should be made to retain the PTFE. PTFE liners are subject to permeation by some corrodents. Table 6.25 provides the vapor permeation of PTFE by selected materials. PTFE is chemically inert in the presence of most corrodents. There are very few chemicals that will attack it within normal use temperatures. These reactants are among the most violent oxidizers and reducing agents known. Elemental sodium in intimate contact with fluorocarbons removes fluorine from the polymer molecule. The other alkali metals (potassium, lithium, etc.) react in a similar manner. Fluorine and related compounds (e.g., chlorine trifluoride) are absorbed into the PTFE resin with such intimate contact that the mixture becomes sensitive to a source of ignition such as impact. The handling of 80% sodium hydroxide, aluminum chloride, ammonia, and certain amines at high temperatures may produce the same effect as elemental sodium. Also slow oxidative attack can be produced by 70% nitric acid under pressure at 4808F (2508C). Refer to Table 6.26 for the compatibility of PTFE with selected corrodents. Reference [1] provides listing of additional corrodents. 6.6.7 Fluorinated Ethylene Propylene Fluorinated ethylene propylene (FEP) has a lower maximum operating temperature than PTFE. It exhibits changes in physical strength after prolonged exposure above 4008F (2048C). Therefore, the recommended maximum continuous operating temperature is 3758F (1908C). Permeation of FEP liners can pose a problem. Table 6.27 provides some permeation data relating to the more common chemicals. There is also some absorption of chemicals by FEP. This absorption can also lead to problems. Table 6.28 is a listing of the absorption of selected liquids by FEP.


368


TABLE 6.23 Compatibility of EHMW PE with Selected Corrodents Maximum Temperature Chemical Acetaldehyde, 40% Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride

8F

8C

90

32

140 140 80

60 60 27

X 120

X 49

150 140 140 80 140

66 60 60 27 60

140 140 140 140

60 60 60 60

140 140

60 60

140 140 140 140 140 140 140 140 140 140 80 140 140

60 60 60 60 60 60 60 60 60 60 27 60 60

140 140 X 130 140 130 140 140

60 60 X 54 60 54 60 60 (continued)


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TABLE 6.23 Continued Maximum Temperature Chemical Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyl phthalate n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% in water Chlorine gas, dry Chlorine gas, wet, 10% Chlorine, liquid Chlorobenzene Chloroform

8F

8C

140 140 140 X X 140 140 170

60 60 60 X X 60 60 77

140 140 X X X X 90 140 80 X 130 140 80 140 140 140 140 140 140 140 140 140

60 60 X X X X 32 60 27 X 54 60 27 60 60 60 60 60 60 60 60 60

X 140 140 X 140 X 140

X 60 60 X 60 X 60

X X 80 120 X X 80

X X 27 49 X X 27 (continued)


370


TABLE 6.23 Continued Maximum Temperature Chemical Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid/conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid

8F

8C

X 140 90

X 60 32

140 140

60 60

140 140 140 80 80

60 60 60 27 27

130 170 73 X 140 140 140 140 140 140 X X 140 140 140 140 140 140 80 X X

54 77 23 X 60 60 60 60 60 60 X X 60 60 60 60 60 60 27 X X

80 X 140 140 140 100 80 X X 80 140

27 X 60 60 60 38 27 X X 27 60 (continued)


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8F

8C

Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

140 140 X X

60 60 X X

140 X 100 100 100 140

60 X 38 38 38 60

140 140 170 170

60 60 77 77

140 140 140 140 140 140 140 80 X X X X 140 X X 140

60 60 60 60 60 60 60 27 X X X X 60 X X 60

140

60



372


TABLE 6.24 Compatibility of HMWPE with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum sulfate Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium gas Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, to 40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde

8F

8C

X 140 140 140 80 X 80 X 150 140 140 110 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 150 80 140 140 140 140 140 X 130 140 130 140 140 140 140 140 X

X 60 60 60 27 X 27 X 66 60 60 43 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 66 27 60 60 60 60 60 X 44 60 44 60 60 60 60 60 X (continued)


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TABLE 6.24 Continued Maximum Temperature Chemical Benzene Benzoic acid Benzyl alcohol Borax Boric acid Bromine gas, dry Bromine gas, moist Bromine, liquid Butadiene Butyl acetate Butyl alcohol n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chloroacetic acid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15% Citric acid, conc. Copper chloride Copper cyanide Copper sulfate Cresol

8F

8C

X 140 X 140 140 X X X X 90 140 X X 140 140 140 140 140 140 140 140 140 140 140 X 140 140 X 140 X 140 X X X X X X X X 140 90 140 140 140 140 140 X

X 60 X 60 60 X X X X 32 60 X X 60 60 60 60 60 60 60 60 60 60 60 X 60 60 X 60 X 60 X X X X X X X X 60 32 60 60 60 60 60 X (continued)


374



8F

8C

Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dibutyl phthalate Dichloroethane Ethylene glycol Ferric chloride Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hypochlorite, 20%

140 140 80 80 80 80 140 140 140 140 X X 140 140 140 140 140 140 140 X 150 80 80 150 140 140 80 X X 80 140 140 X X 120 140 X 100 100 100 140 140 140 140 150 150 140

60 60 27 27 27 27 60 60 60 60 X X 60 60 60 60 60 60 60 X 66 27 27 66 60 60 27 X X 27 60 60 X X 49 60 X 38 38 38 60 60 60 60 66 66 60 (continued)


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8F

8C

Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid Zinc chloride

140 140 140 140 140 140 80 X X X X 140 X X 80 140

60 60 60 60 60 60 27 X X X X 60 X X 27 60


TABLE 6.25 Vapor Permeation PTFE Permeation (g 100 in.2/24 h/mil) at Gases Carbon dioxide Helium Hydrogen chloride, anhy. Nitrogen Acetophenone Benzene Carbon tetrachloride Ethyl alcohol Hydrochloric acid, 20% Piperdine Sodium hydroxide, 50% Sulfuric acid, 98%

738F(238C)

0.56 0.36 0.06 0.13 !0.01 0.07 5!10K5 1.8!10K5

868F(308C) 0.66 0.22 !0.01 0.11


0.80

376


TABLE 6.26 Compatibility of PTFE with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aqueous Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gasa Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 (continued)


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TABLE 6.26 Continued Maximum Temperature Chemical a

Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, drya Bromine liquida Butadienea Butyl acetate Butyl alcohol Butyl phthalate n-Butylamine Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfidea Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachlorideb Carbonic acid Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, weta Chlorine, liquid Chlorobenzenea Chloroforma Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromyl chloride Citric acid, 15% Citric acid, conc.

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 X 450 X 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 X 232 X 232 232 232 232 232 232 232 232 (continued)


378


TABLE 6.26 Continued Maximum Temperature Chemical Copper carbonate Copper chloride Copper cyanide, 10% Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride)a Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil.a,b Hydrobromic acid, 20%b Hydrobromic acid, 50%b Hydrochloric acid, 20%b Hydrochloric acid, 38%b Hydrocyanic acid, 10% Hydrofluoric acid, 100%a Hydrofluoric acid, 30%a Hydrofluoric acid, 70%a Hypochlorous acid Iodine solution, 10%a Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloridea Methyl ethyl ketonea Methyl isobutyl ketoneb Muriatic acida Nitric acid, 5%a Nitric acid, 20%a Nitric acid, 70%a Nitric acid, anhydrousa Nitrous acid, 10% Oleum Perchloric acid, 10% Perchloric acid, 70%

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 X X 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 X X 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 (continued)


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8F

8C

Pheno Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuminga Sulfurous acid Thionyl chloride Toluenea Trichloroacetic acid White liquor Zinc chloridec

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232

a

The chemicals listed are in the pure state or in saturated solution unless otherwise indicated. Compatibilty is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. A blank space indicates that the data is unavailable. a Material will permeate. b Material will cause stress cracking. c Material will be absorbed. Source: From P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.

FEP basically has the same corrosion resistance properties as PTFE but at lower maximum temperatures. It is resistant to practically all chemicals, the exception being extremely potent oxidizers such as chlorine trifluoride and related compounds. Some chemicals will attack FEP when present in high concentrations, at or near the service temperature limit. Refer to Table 6.29 for the compatibility of FEP with selected corrodents. Reference [1] provides additional listings.


380


TABLE 6.27 Vapor Permeation of FEP Permeation (g 100 in.2/24 h/mil) at: 738F(238C) Gases Nitrogen Oxygen Vapors Acetic acid Acetone Acetophenone Benzene n-Butyl ether Carbon tetrachloride Decane Ethyl acetate Ethyl alcohol Hexane Hydrochloric acid, 20% Methanol Sodium hydroxide, 50% Sulfuric acid, 98% Toluene Water

958F(358C)

1228F(508C)

0.42 0.95

3.29

0.18 0.39 0.13 0.47 0.15 0.08 0.11 0.72 0.06 0.11 0.01 4!10K5 8!10K6 0.37 0.09

0.64 0.31

1.03 2.9

0.77 0.69 0.57

5.61 2.93 0.89

0.45

TABLE 6.28 Absorption of Selected Liquida by FEP Chemical Aniline Acetophenone Benzaldehyde Benzyl alcohol n-Butylamine Carbon tetrachloride Dimethylsulfoxide Nitrobenzene Perchlorethylene Sulfuryl chloride Toluene Tributyl phosphateb a b

Temperature (8F/8C)

Range of Weight Gains (%)

365/185 394/201 354/179 400/204 172/78 172/78 372/190 410/210 250/121 154/68 230/110 392/200

0.3–0.4 0.6–0.8 0.4–0.5 0.3–0.4 0.3–0.4 2.3–2.4 0.1–0.2 0.7–0.9 2.0–2.3 1.7–2.7 0.7–0.8 1.8–2.0

16 h exposure at their boiling points. Not boiling.


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TABLE 6.29 Compatibility of FEP with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 10% Acetic acid, 50% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylic acid Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum acetate Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoridea Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gasa Ammonium bifluoridea Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10%a Ammonium fluoride, 25%a Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Ammonium sulfite Amyl acetate Amyl alcohol Amyl chloride Anilineb Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride

8F

8C

200 400 400 400 400 400 400 400 400 200 400 400 400 400 400 400 400 300 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 250 400 400 400

93 204 204 204 204 204 204 204 204 93 204 204 204 204 204 204 204 149 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 121 204 204 204 (continued)


382



8F

8C

Barium hydroxide Barium sulfate Barium sulfide Benzaldehydeb Benzene sulfonic acid, 10% Benzeneb Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, drya Bromine gas, moista Bromine liquida,b Butadienea Butyl acetate Butyl alcohol Butyl phthalate n-Butylamineb Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfidea Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloridea,b,c Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, weta Chlorine, liquidb Chlorobenzenea Chloroforma

400 400 400 400 400 400 400 400 400 400 400 200 200 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 X 400 400 400 400

204 204 204 204 204 204 204 204 204 204 204 93 93 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 X 204 204 204 204 (continued)


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Chlorosulfonic acid Chromic acid, 50%b Chromic acid, 10% Chromyl chloride Citric acid, 15% Citric acid, conc. Copper acetate Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride)a Ethylene glycol Ferric chloride Ferric chloride, 50% in waterb Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20%a,c Hydrobromic acid, 50%a,c Hydrochloric acid, 20%a,c Hydrochloric acid, 38%a,c Hydrocyanic acid, 10% Hydrofluoric acid, 30%a Hydrofluoric acid, 70%a Hydrofluoric acid, 100%a Hypochlorous acid Iodine solution, 10% Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloridea Methyl ethyl ketonea Methyl isobutyl ketonea Muriatic acida

8F

8C

400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 260 260 400 400 200 X 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 300 400 400 400 400

204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 127 127 204 204 93 X 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 149 204 204 204 204 (continued)


384


TABLE 6.29 Continued Maximum Temperature Chemical a

Nitric acid, 5% Nitric acid, 20%a Nitric acid, 70%a Nitric acid, anhydrousa Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenola Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Silver bromide, 10% Sodium carbonate Sodium chloride Sodium hydroxide, 10%b Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 50% Sulfuric acid, 10% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fumingc Sulfurous acid Thionyl chloridea Toluene Trichloroacetic acid White liquor Zinc chloridec

8F

8C

400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400 400

204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204 204

The chemicals listed are in the pure state or in saturated solution unless otherwise indicated. Compatibilty is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. A blank space indicates that the data is unavailable. a b c

Material will cause stress cracking. Material will permeate. Material will be absorbed.



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TABLE 6.30 Permeation of Various Gases in PFA at 778F (258C) Gas

Permeation (cm3 mil thickness/100 in.2 24 h atm)

Carbon dioxide Nitrogen Oxygen

2260 291 881

6.6.8 Perfluoralkoxy Perfluoralkoxy (PFA) can be continuously used at 5008F (2608C). It is subject to permeation by certain gases and will absorb liquids. Table 6.30 illustrates the permeability of PFA, and Table 6.31 lists the absorption of representative liquids by PFA. Perfluoralkoxy is inert to strong mineral acids, inorganic bases, inorganic oxidizers, aromatics, some aliphatic hydrocarbons, alcohols, aldehydes, ketones, esters, ethers, chlorocarbons, fluorocarbons, and mixtures of these compounds. TABLE 6.31 Absorption of Representative Liquids in PFA Liquidsa

Temperature, 8F/8C

Range of Weight Gains, %

Aniline Acetophenone Benzaldehyde Benzyl alcohol n-Butylamine Carbon tetrachloride Dimethyl sulfoxide Freon 113 Isooctane Nitrobenzene Perchlorethylene Sulfuryl chloride Toluene Tributyl phosphate Bromine, anhydrous Chlorine, anhydrous Chlorosulfonic acid Chromic acid, 50% Ferric chloride Hydrochloric acid, 37% Phosphoric acid, conc. Zinc chloride

365/185 394/201 354/179 400/204 172/78 172/78 372/190 117/47 210/99 410/210 250/121 154/68 230/110 392/200b K5/K22 248/120 302/150 248/120 212/100 248/120 212/100 212/100

0.3–0.4 0.6–0.8 0.4–0.5 0.3–0.4 0.3–0.4 2.3–2.4 0.1–0.2 1.2 0.7–0.8 0.7–0.9 2.0–2.3 1.7–2.7 0.7–0.8 1.8–2.0 0.5 0.5–0.6 0.7–0.8 0.00–0.01 0.00–0.01 0.00–0.03 0.00–0.01 0.00–0.03

a

Liquids were exposed for 168 hours at the boiling point of the solvents. The acidic reagents were exposed for 168 hours. b Not boiling.


386


PFA will be attacked by certain halogenated complexes containing fluorine. These include chlorine trifluoride, bromine trifluoride, iodine pentafluoride, and fluorine. PFA can also be attacked by such metals as sodium or potassium, particularly in the molten state. PFA has the advantage over PTFE in that it can be thermoformed, heat sealed, welded, and heat laminated. This makes the material much easier to produce lining from than that of PTFE. PFA can be bonded to a metal substrate. Refer to Table 6.32 for the compatibility of PFA with selected corrodents. Reference [1] provides additional listings. 6.6.9 Ethylene Tetrafluoroethylene Ethylene Tetrafluoroethylene (ETFE) is sold under the trade name of Tefzel by DuPont. It is a partially fluorinated copolymer of ethylene and tetrafluoroethylene with a maximum service temperature of 3008F/1498C. Tefzel can be melt bonded to untreated aluminum, steel, and copper. It can also be melt bonded to itself. To adhesive bond Tefzel with polyester or epoxy compounds, the surface must be chemically etched or subjected to corona or flame treatments. ETFE is a rugged thermoplastic. It is less dense, tougher, stiffer, and exhibits a higher tensile strength and creep resistance than PTFE and FEP fluorocarbon resins. Vapor permeation of ETFE is as follows: Gas

Permeation (cm3 mil thickness/100 in.2 24 h atm)

Carbon dioxide Nitrogen Oxygen Helium

250 30 100 900

Tefzel is inert to strong mineral acids, inorganic bases, halogens, and metal salt solutions. Even carboxylic acids, anhydrides, aromatic and aliphatic hydrocarbons, alcohols, ketones, ethers, esters, chlorocarbons, and classic polymer solvents have little effect on ETFE. Very strong oxidizing acids near their boiling points, such as nitric acid, at high concentration will affect ETFE in varying degrees as well as organic bases such as amines and sulfonic acids. Refer to Table 6.33 or the compatibility of ETFE with selected corrodents. Reference [1] provides a more comprehensive listing. 6.6.10 Chlorotrifluoroethylene Chlorotrifluoroethylene (ECTFE) is sold under the tradename of Halar by Ausimont USA, Inc. Halar has many of the desirable properties of PTFE


Sheet Linings

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TABLE 6.32 Compatibility of PFA with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aqueous Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gasb Ammonium bifluorideb Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10%b Ammonium fluoride, 25%b Ammonium hydroxide, 250% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Anilinea Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehydea

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 (continued)


388



Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chlorideb Borax Boric acid Bromine gas, dry Bromine liquida,b Butadieneb Butyl acetate Butyl alcohol Butyl phthalate n-Butylaminea Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfideb Carbon dioxide, dry Carbon dioxide, wet Carbon disulfideb Carbon monoxide Carbon tetrachloridea,b,c Carbonic acid Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wetb Chlorine, liquida Chlorobenzeneb Chloroformb Chlorosulfonic acida Chromic acid, 10% Chromic acid, 50%a Chromyl chloride Citric acid, 15% Citric acid, conc.

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 X 450 X 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 X 232 X 232 232 232 232 233 232 232 232 (continued)


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TABLE 6.32 Continued Maximum Temperature Chemical Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Dichloroacetic acid Dichloroethane (ethylene dichloride)b Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hvdrochloric acid, 20%b,c Hydrobromic acid, 20%b,c Hydrobromic acid, 50%b,c Hydrobromic acid, 20%b,c Hydrochloric acid, 38%b,c Hydrocyanic acid, 10% Hydrofluoric acide, 30%b Hydrofluoric acid, 70%b Hydrofluoric acid, 100%b Hypochlorous acid Iodine solution, 10%b Ketones, general Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chlorideb Methyl ethyl ketoneb Methyl isobutyl ketoneb Muriatic acidb Nitric acid, 5%b Nitric acid, 20%b Nitric acid, 70%b Nitric acid, anhydrousb Nitrous acid, 10% Oleum Perchloric acid, 10% Perchloric acid, 70%

8F

8C

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 X X 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 233 232 232 X X 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 (continued)


390



8F

8C

Phenol Phosphoric acid, 50–80%a Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chlorideb Tolueneb Trichloroacetic acid White liquor Zinc chloridea

450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450

232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232 232

b


Material will be absorbed. Material will permeate. Material will cause stress cracking.


without some of the disadvantages. ECTFE can be welded with ordinary thermoplastic welding equipment. It is used to line vessels and pipe. Liner thicknesses are usually 0.160 in. thick, that resists permeation. The water absorption rate of ECTFE is low, being less than 0.1%. Halar has a broad use temperature range from cryogenic to 3408F/1718C with continuous service to 3008F/1498C. It exhibits excellent impact strength


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TABLE 6.33 Compatibility of ETFE with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetamide Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Allyl chloride Alum Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene

8F

8C

200 250 250 250 230 230 300 150 150 150 280 210 190 300 300 300 300 300 300 300 300 300 300 300 290 300 300 300 300 300 230 300 300 300 300 250 300 300 230 210 210 300 300 300 300 300 210 210

93 121 121 121 110 110 149 66 66 66 138 99 88 149 149 149 149 149 149 149 149 149 149 149 143 149 149 149 149 149 110 149 149 149 149 121 149 149 110 99 99 149 149 149 149 149 99 99 (continued)


392



8F

8C

Benzene sulfonic acid, 10% Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine water, 10% Butadiene Butyl acetate Butyl alcohol Butyl phthalate n-Butylamine Butyric acid Calcium bisulfide Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid, 50% Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet Chlorine, water Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Chromic chloride Citric acid, 15% Copper chloride Copper cyanide Copper sulfate Cresol

210 270 300 300 300 300 150 230 250 230 300 150 120 250 300 300 300 300 300 300 300 300 260 300 210 150 300 300 150 300 270 300 300 230 230 210 250 100 210 230 80 150 150 210 120 300 300 300 270

99 132 149 149 149 149 66 110 121 110 149 66 49 121 149 149 149 149 149 149 149 149 127 149 99 66 149 149 66 149 132 149 149 110 110 99 121 38 99 110 27 66 66 99 49 149 149 149 132 (continued)


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TABLE 6.33 Continued Maximum Temperature Chemical Cupric chloride, 5% Cyclohexane Cyclohexanol Dichloroacetic acid Ethylene glycol Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Manganese chloride Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hypochlorite, 20% Sodium hypochlorite, conc.

8F

8C

300 300 250 150 300 300 300 300 300 100 100 300 300 300 300 300 300 270 250 230 300 250 250 300 270 120 300 230 300 300 150 150 80 X 210 150 230 150 210 270 130 300 250 300 300 230 230 300 300

149 149 121 66 149 149 149 149 149 38 38 149 149 149 149 149 149 133 121 110 149 121 121 149 132 49 149 110 149 149 66 66 27 X 99 66 110 66 99 132 54 149 121 149 149 110 110 149 149 (continued)


394


TABLE 6.33 Continued Maximum Temperature Chemical Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid Zinc chloride

8F

8C

300 300 300 300 300 300 300 300 300 120 210 210 250 210 300

149 149 149 149 149 149 149 149 149 49 99 99 121 99 149

The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature for which data is available. Incompatibility is shown by an X. A blank space indicates that the data is unavailable. Source: Material extracted from P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.

and abrasion resistance over its entire operating range, and good tensile, flexural, and wear related properties. Halar is very similar in its corrosion resistance to PTFE, but it does not have the permeation problem associated with PTFE, PFA, and FEP. It is resistant to strong mineral and oxidizing acids, alkalies, metal etchants, liquid oxygen, and practically all organic solvents except hot amines, aniline, dimethylamine, etc. ECTFE is not subject to chemically induced stress cracking from strong acids, bases, or solvents. Some halogenated solvents can cause ECTFE to become slightly plasticized when it comes into contact with them. Under normal circumstances, this does not affect the usefulness of the polymer because upon removal of the solvent from contact and upon drying, its mechanical properties return to their original values, indicating that no chemical attack has taken place. Like other fluoropolymers, ECTFE will be attacked by metallic sodium and potassium. Table 6.34 provides the compatibility of ECTFE with selected corrodents. Reference [1] provides a more comprehensive listing of corrosion resistance.


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TABLE 6.34 Compatibility of ECTFE with Selected Corrodents Maximum Temperature Chemical

8F

8C

Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl chloride Alum Aluminum chloride, aqueous Aluminum chloride, dry Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, 10% Ammonium chloride, 50% Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10%

250 250 150 200 100 150 150 150 150 300 300 300

121 121 66 93 38 66 66 66 66 149 149 149

300 300 300 150 300 300 300 300 290 300 300 300 300 300 300 300 150 300 300 300 160 300 300 90 100 250 300 300 300 300 300 150 150 150

149 149 149 66 149 149 149 149 143 149 149 149 149 149 149 149 66 149 149 149 71 149 149 32 38 121 149 149 149 149 149 66 66 66 (continued)


396



8F

8C

Benzoic acid Benzyl alcohol Benzyl chloride Borax Boric acid Bromine gas, dry Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyric acid Calcium bisulfide Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Citric acid, 15% Citric acid, conc. Copper carbonate Copper chloride Copper cyanide Copper sulfate

250 300 300 300 300 X 150 250 150 300 250 300 300 300 300 300 300 300 300 300 300 300 220 80 300 300 80 150 300 300 300 250 250 150 250 250 150 250 80 250 250 300 300 150 300 300 300

121 149 149 149 149 X 66 121 66 149 121 149 149 149 149 149 149 149 149 149 149 149 104 27 149 149 27 66 149 149 149 121 121 66 121 121 66 121 27 121 121 149 149 66 149 149 149 (continued)


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8F

8C

Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 70% Hydrofluoric acid, 100% Hypochlorous acid Iodine solution, 10% Lactic acid, 25% Lactic acid, conc. Magnesium chloride Malic acid Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Nitrous acid, conc. Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride

300 300 300 300 300 300 300 300 300 300 300 X 80 300 300 300 300 300 300 250 240 240 300 250 150 150 300 250 300 150 150 300 300 250 150 150 250 X 150 150 150 250 80 300 250 300 300

149 149 149 149 149 149 149 149 149 149 149 X 27 149 149 149 149 149 149 121 116 116 149 121 66 66 149 121 149 66 66 149 149 121 66 66 121 X 66 66 66 121 27 149 121 149 149 (continued)


398


TABLE 6.34 Continued Maximum Temperature Chemical Sodium hydroxide, 10% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 20% Sodium hypochlorite, conc. Sodium sulfide, to 50% Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid White liquor Zinc chloride

8F

8C

300 250 150 300 300 300 300 300 250 250 250 150 150 80 300 250 150 150 150 250 300

149 121 66 149 149 149 149 149 121 121 121 66 66 27 149 121 66 66 66 121 149


6.6.11 Polyvinylidene Chloride (Saran) Saran is the trademark of Dow Chemical for their proprietary polyvinylidene chloride (PVDC) resin. It has a maximum allowable operating temperature of 1758F/818C. It is used to line piping as well as vessels. PVDC has found wide application in the plating industry and for handling deionized water, Pharmaceuticals, food processing, and other applications where stream purity protection is critical. The material complies with FDA regulations for food processing and potable water and also with regulations prescribed by the Meat Inspection Division of the Department of Agriculture for transporting fluids used in meat production. In applications such as plating solutions, chlorines, and certain other chemicals, Saran is superior to polypropylene and finds many applications in the handling of municipal water supplies and waste waters. Refer to Table 6.35 for the compatibility of PVDC with selected corrodents. Reference [1] provides a more comprehensive listing.


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TABLE 6.35 Compatibility of Polyvinylidene Chloride (Saran) with Selected Corrodents Maximum Temperature Chemical Acetaldehyde Acetic acid, 10% Acetic acid, 50% Acetic acid, 80% Acetic acid, glacial Acetic anhydride Acetone Acetyl chloride Acrylonitrile Adipic acid Allyl alcohol Alum Aluminum chloride, aqueous Aluminum fluoride Aluminum hydroxide Aluminum nitrate Aluminum oxychloride Aluminum sulfate Ammonia gas Ammonium bifluoride Ammonium carbonate Ammonium chloride, sat. Ammonium fluoride, 10% Ammonium fluoride, 25% Ammonium hydroxide, 25% Ammonium hydroxide, sat. Ammonium nitrate Ammonium persulfate Ammonium phosphate Ammonium sulfate, 10–40% Ammonium sulfide Amyl acetate Amyl alcohol Amyl chloride Aniline Antimony trichloride Aqua regia, 3:1 Barium carbonate Barium chloride Barium hydroxide Barium sulfate Barium sulfide Benzaldehyde Benzene Benzene sulfonic acid, 10% Benzoic acid Benzyl chloride

8F

8C

150 150 130 130 140 90 90 130 90 150 80 180 150 150 170 180 140 180 X 140 180 160 90 90 X X 120 90 150 120 80 120 150 80 X 150 120 180 180 180 180 150 X X 120 120 80

66 66 54 54 60 32 32 54 32 66 27 82 66 66 77 82 60 82 X 60 82 71 32 32 X X 49 32 66 49 27 49 66 27 X 66 49 82 82 82 82 66 X X 49 49 27 (continued)


400


TABLE 6.35 Continued Maximum Temperature Chemical Boric acid Bromine liquid Butadiene Butyl acetate Butyl alcohol Butyl phthalate Butyric acid Calcium bisulfite Calcium carbonate Calcium chlorate Calcium chloride Calcium hydroxide, 10% Calcium hydroxide, sat. Calcium hypochlorite Calcium nitrate Calcium oxide Calcium sulfate Caprylic acid Carbon bisulfide Carbon dioxide, dry Carbon dioxide, wet Carbon disulfide Carbon monoxide Carbon tetrachloride Carbonic acid Cellosolve Chloracetic acid Chloracetic acid, 50% water Chlorine gas, dry Chlorine gas, wet Chlorine, liquid Chlorobenzene Chloroform Chlorosulfonic acid Chromic acid, 10% Chromic acid, 50% Citric acid, conc. Citric, acid, 15% Copper carbonate Copper chloride Copper cyanide Copper sulfate Cresol Cupric chloride, 5% Cupric chloride, 50% Cyclohexane Cyclohexanol

8F

8C

170 X X 120 150 180 80 80 180 160 180 160 180 120 150 180 180 90 90 180 80 80 180 140 180 80 120 120 80 80 X 80 X X 180 180 180 180 180 180 130 180 150 160 170 120 90

77 X X 49 66 82 27 27 82 71 82 71 82 49 66 82 82 32 32 82 27 27 82 60 82 27 49 49 27 27 X 27 X X 82 82 82 82 82 82 54 82 66 71 77 49 32 (continued)


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8F

8C

Dichloroacetic acid Dichloroethane (ethylene dichloride) Ethylene glycol Ferric chloride Ferric chloride, 50% in water Ferric nitrate, 10–50% Ferrous chloride Ferrous nitrate Fluorine gas, dry Fluorine gas, moist Hydrobromic acid, dil. Hydrobromic acid, 20% Hydrobromic acid, 50% Hydrochloric acid, 20% Hydrochloric acid, 38% Hydrocyanic acid, 10% Hydrofluoric acid, 30% Hydrofluoric acid, 100% Hypochlorous acid Ketones, general Lactic acid, conc. Magnesium chloride Malic acid Methyl chloride Methyl ethyl ketone Methyl isobutyl ketone Muriatic acid Nitric acid, 5% Nitric acid, 20% Nitric acid, 70% Nitric acid, anhydrous Oleum Perchloric acid, 10% Perchloric acid, 70% Phenol Phosphoric acid, 50–80% Picric acid Potassium bromide, 30% Salicylic acid Sodium carbonate Sodium chloride Sodium hydroxide, 0% Sodium hydroxide, 50% Sodium hydroxide, conc. Sodium hypochlorite, 10% Sodium hypochlorite, conc. Sodium sulfide, to 50%

120 80 180 140 140 130 130 80 X X 120 120 130 180 180 120 160 X 120 90 80 180 80 80 X 80 180 90 150 X X X 130 120 X 130 120 110 130 180 180 90 150 X 130 120 140

49 27 82 60 60 54 54 27 X X 49 49 54 82 82 49 71 X 49 32 27 82 27 27 X 27 82 32 66 X X X 54 49 X 54 49 43 54 82 82 32 66 X 54 49 60 (continued)


402


TABLE 6.35 Continued Maximum Temperature Chemical Stannic chloride Stannous chloride Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfuric acid, 100% Sulfuric acid, fuming Sulfurous acid Thionyl chloride Toluene Trichloroacetic acid Zinc chloride

8F

8C

180 180 120 X X X X X X 80 X 80 80 170

82 82 49 X X X X X X 27 X 27 27 77


Reference 1.

P.A. Schweitzer. 2004. Corrosion Resistance Tables, Vols. 1–4, 5th ed., New York: Marcel Dekker.


7 Coatings

7.1 Introduction to Coatings Construction metals are selected because of their mechanical properties and machineability at a low price, although, they should also be corrosion resistant. Very seldom can these properties be met in one and the same material. This is where coatings come into play. By applying an appropriate coating, the base metal with the good mechanical properties can be utilized while the appropriate coating provides corrosion protection. The majority of coatings are applied on external surfaces to protect the metal from natural atmospheric corrosion, and atmospheric pollution. On occasion, it may also be necessary to provide protection from accidental spills and/or splashes. In some instances, coatings are applied internally in vessels for corrosion resistance. There are basically four different classes of coatings: Organic

Inorganic

Conversion

Coal tars Phenolics Vinyls Acrylics Epoxy Alkyds Urethanes

Silicates Ceramics Glass

Anodizing Phosphating Chromate Molybdate

a

Metallica Galvanizing Vacuum vapor deposition Electroplating Diffusion

These are processes rather than individual coatings because many metals may be applied by each process. The process and item to be coated will determine which metal will be used.

7.1.1 Principles of Corrosion Protection Most metals used for construction purposes are unsuitable in the atmosphere. These unstable metals are produced by reducing ores

403

CAT8247—CHAPTER 7—17/10/2006—15:01—TRGANESH—XML MODEL B – pp. 403–485

404


artificially; therefore, they will return to their original ores or to similar metallic compounds when exposed to the atmosphere. For example, metallic iron is oxidized to ferric oxyhydride in a thermodynamically stable state (iron in the higher level of free energy is changed to lepidocrocite, g-FeOOH, in the lower level): 4Fe C 3O2 C 2H2 O/ 4FeOOH This reaction of a metal in a natural environment is called corrosion. By means of a coating a longer period of time is required for rust to form on the substrate, as shown in Figure 7.1. Therefore, it is important that the proper coating material be selected for application in the specific environment. For a coating to be effective, it must isolate the base metal from the environment. The service life of a coating is dependent upon the thickness and the chemical properties of the coating layer. The latter determines the durability of a coating material in a specific environment that is the corrosion resistance of a metal coating or the stability of its organic and inorganic compounds. In order to be effective, the coating’s durability must be greater than that of the base metal’s, or it must be maintained by some means. In addition, a coating is often required to protect the base metal with its original pore and crack or with a defect that may have resulted from mechanical damage and/or pitting corrosion. Coatings are classified according to the electrochemical principle that they operate on to provide protection. These categories are: 1. EMF control 2. Cathodic control protection 3. Anodic control protection 4. Mixed control protection

Lifetime of coating 0

o

Free energy change, ∆G , k-cal/mole

5. Resistance control protection

Uncoated steel

−0.1

Coated steel

FeOOH line

Exposure time

FIGURE 7.1 Role of corrosion resistant coating.


Coatings

405

The mechanism of the corrosion cell can explain the theories that these five categories operate on. 7.1.2 Corrosion Cell A corrosion cell is formed on a metal surface when oxygen and water are present. Refer to Figure 7.2. The electrochemical reactions taking place in the corrosion cell are: Anodic reaction (MZmetal): M/ MnC C ne

(7.1)

Cathode area Anode area

Metal

Air o2

o2

Electrolyte OH −

M n+

e

OH − e

Metal FIGURE 7.2 Structure of corrosion cell.


406


Cathodic reaction in acidic solution: 2HC C 2e/ H2

(7.2)

Cathodic reaction in neutral and alkaline solutions: O2 C 2H2 O C 4e/ 4OHK

(7.3)

The Evans diagram shown in Figure 7.3 represents the mechanism of the corrosion cell. The cathodic current is expressed in the same direction as the anodic current. In Figure 7.3, Ea shows the single potential for H2/HC or for O2/OHK at the cathode and Ea shows the single potential for metal/metal in equilibria at the anode. The single potential is given by the Nernst equation: E Z E8 C

RT ln a nF

(7.4)

where EZ single potential E8Z standard single potential R Z absolute temperature nZ charge on an ion FZ Faraday constant aZ activity of the ion

Internal polarization curve

Electrode potential

Ec

O 2+ 2H 2O

+4

nc

e 4O H−

Ecorr n+

M

M

Ea

ioc

ioa

External polarization curve

e

−n

tho

dic

rve

cu

riz

ola

p dic

o An Ca

na

on ati

po

lar

iza

tio

nc

urv e

icorr

FIGURE 7.3 Mechanism of corrosion cell.


Coatings

407

When aZ1, E is equal to E8. The standard single potential E8 shows the degree of activity of the metal and gas. The electrochemical series consists of the arrangement of metals in order of electrode potential. The more negative the single potential is, the more active the metal. Table 7.1 provides the standard single potentials of various metals and nonmetal reactants. When the electromotive force (EcKEa) is supplied, the corrosion cell is formed with the current flowing between the anode and the cathode. The cathodic electrode potential is shifted to the less noble direction. The shifting of potentials is called cathodic and anodic polarization. The reaction rate curves (EKi) are known as cathodic or anodic polarization curves. The corrosion potential Eccorr and the corrosion current icorr are given by the intersection of the cathodic and anodic polarization curves—indication that both electrodes react at the same rate in the corrosion process. The polarization curves in the current density range greater than icorr are called external polarization curves, and those in the current density range less than icorr are called internal polarization curves. By sweeping the electrode potential from the corrosion potential to the cathodic or anodic

TABLE 7.1 Standard Single Potentials, E8 (V, SHE, 258C) Active Electrode C

Li/Li Rb/RbC Cs/CsC K/KC Ba/Ba2C Sr/Sr2C Ca/CaC Na/NaC Mg/Mg2C Th/Th4C Ti/Ti2C Be/Be2C Al/Al3C V/V2C Mn/Mn2C Zn/Zn2C Cr/Cr3C Fe/Fe2C Cd/Cd In/In3C Ti/TiC Co/Co2C Ni/Ni2C

Inert E8 K3.01 K0.298 K0.292 K2.92 K2.92 K2.89 K2.84 K2.71 K2.38 K2.10 K1.75 K1.70 K1.66 K1.5 K1.05 K0.763 K0.71 K0.44 K0.402 K0.34 K0.335 K0.27 K0.23

Electrode 3C

E8

Mo/Mo Sn/Sn2C Pb/Pb2C H2/HC Bi/BiO Cu/Cu2C Rh/Rh2C Hg/HgC Ag/AgC Pd/Pd2C Ir/Ir3C Pt/Pt2C Au/Au3C Au/AuC

K0.2 K0.140 K0.126 G0 C0.32 C0.34 C0.6 C0.798 C0.799 C0.83 C1.0 C1.2 C1.42 C1.7

O2/OH I2/IK Br2/BrK Cl2/ClK F2/FK S/S2K Se/Se2C Te/Te2C

C0.401 C0.536 C1.066 C1.256 C2.85 K0.51 K0.78 K0.92


408


direction, the external polarization curve can be determined. The internal polarization curve cannot be directly measured by the electrochemical technique because it is impossible to pick up the current separately from the anode and cathode that exist in the electrode. By analyzing the metallic ions dissolved and the oxidizer reaction, the internal polarization curves can be determined. Anodic or cathodic overpotential is represented by the difference in potential between Ecorr and Ea or Ecorr and Ec and is expressed as na or nc, where na Z Ecorr KEa

na O 0

(7.5)

nc Z Ecorr KEc

nc ! 0:

(7.6)

The anodic and cathodic resistance is represented by na/icorr. As soon as the cell circuit is formed, the corrosion reaction starts. Ec KEa Z ½nc Kicorr R;

(7.7)

where R is the resistance of the electrolyte between the anode and cathode. As the current passes through three processes (the anodic process, the cathodic process, and the transit process in the electrolytes), the electromotive force of a corrosion cell is dissipated. When the electrode is polarized, the overpotential n is composed of the activation overpotential na and the concentration overpotential nc. n Z na C nc :

(7.8)

The activation overpotential na results from the potential energy barrier to be overcome for a charge to cross the double layer at the interface (MZMnCCne) and is given as follows: In the anodic reaction: naa Z ba log

ia ioa

ðTafel equationÞ

ba Z 2:3

RT : anF

(7.9) (7.10)

In the cathodic reaction: nac Z bc log

ic ioc

bc Z

ðTafel equationÞ 2:3RT ; ð1KaÞnF


(7.11) (7.12)

Coatings

409

where naa Z activation overpotential in the anodic reaction nac Z activation overpotential in the cathodic reaction ba Z anodic Tafel coefficient bc Z cathodic Tafel coefficient a Z transfer coefficient ia Z anodic current density ic Z cathodic current density ioa Z exchange current density of anode ioc Z exchange current density of cathode The degree of contribution of electrical energy for the activation energy in the electrode reaction (0!a!1) is indicated by the energy transfer factor a, that, in most cases, is in the range of 0.3–0.7. The exchange current density ia or ic is the flux of charge that passes through the electrical double layer at the single-equilibrium potential Ea or Ec. A linear relationship exists between na and log ia or log ic. The Tafel coefficient ba or bc is the slope dna/d (log ia or log ic) of the polarization curve. Therefore, b is one of the important factors controlling the corrosion rate. The electrode reaction at the low reaction rate is controlled by the activation overpotential. One of the processes controlled by the activation overpotential is the cathodic reaction (in the acid solution): 2HC C 2e Z H2 :

(7.13)

Table 7.2 shows the hydrogen overpotentials of various metals. The activation overpotential varies with the kind of metal and the electrolyte

TABLE 7.2 Hydrogen Overpotentials of Various Metals

Metal

Temperature (8C)

Pt smooth Mo Au Ag Ni Bi Fe Cu Al Sn Cd Zn Pb

20 20 20 20 20 20 16 20 20 20 16 20 20

Solutions 1 N HCl 1 N HCl 1 N HCl 0.1 N HCl 0.1 N HCl 1 N HCl 1 N HCl 0.1 N HCl 2 N H2SO4 1 N HCl 1 N HCl 1 N H2SO4 0.01–8 N HCl

Hydrogen Overpotential jn8j (V/mA/ cmL2)

Tatel Coefficient jbcj (V)

Exchange Current Density jiocj (A/cm2)

0.00 0.12 0.15 0.30 0.31 0.40 0.45 0.44 0.70 0.75 0.80 0.94 1.16

0.03 0.04 0.05 0.09 0.10 0.10 0.15 0.12 0.10 0.15 0.20 0.12 0.12

10K3 10K6 10K6 5!10K7 8!10K7 10K7 10K6 2!10K7 10K10 10K8 10K7 1.6!10K11 2!1013


410


condition. Metal dissolution and metal ion deposition are usually controlled by the activation overpotential. The anodic overpotential is given by na Z ba log

ia : ioa

(7.14)

At high reaction rates, the concentration overpotential nc becomes the controlling factor in the electrode reaction. In this case, the electrode reaction is controlled by mass transfer process that is the diffusion rate of reactive species. The diffusion current i is given as follows: iZ

nFDðCKC0 Þ ; d

(7.15)

where i Zcurrent density D Zdiffusion coefficient C Zconcentration of reactive species in the bulk solution C0 Zconcentration of reactive species at the interface d Zthickness of the diffusion layer. When the concentration of the reactive species at the interface is zero, C0Z0, and the current density reaches a critical value, iL called the limiting current density: iL Z

nFDC : d

(7.16)

From Equation 7.15 and Equation 7.16, C0 i Z1Z : C iL

(7.17)

The concentration overpotential is given as follows: nc Z 2:3

RT C log 0 : nF C

(7.18)

From Equation 7.17 and Equation 7.18, nc Z

2:3RT i log 1K : nF iL

(7.19)

As seen in Equation 7.19, the concentration overpotential increases rapidly as i approaches iL.


Coatings

411

The cathodic reaction is controlled by the activation overpotential nac and the concentration overpotential nac . The cathodic overpotential is nc Z nac C ncc :

(7.20)

The cathodic overpotential nc can be written in the form: nc Z bc log

ic 2:3RT i C log 1K c : ioc nF icL

(7.21)

See Equation 7.12, Equation 7.19, and Equation 7.20. In most cases, the corrosion rate can be determined from the anodic and cathodic overpotentials since the rate determining process is determined by the slopes of the two polarization curves. As previously mentioned, the role of the coating is to isolate the substrate from the environment. The coating accomplishes this based on two characteristics of the coating material: (1) the corrosion resistance of the coating material when the coating is formed by the defect free continuous layer and (2) the electrochemical action of the coating material when the coating layer has some defect such as a pore or crack. The mechanism of the corrosion cell can explain the action required of the coating layer. For better understanding, Equation 7.7 is rewritten as follows: icorr Z

ðEc KEa ÞKjnc jna : R

(7.22)

A corrosion resistant coating is achieved by one of the five different methods to decrease icorr based on Equation 7.22: 1. EMF control protection: Decrease in electromotive force (EcKEa) 2. Cathodic control protection: Increase in cathodic overpotential jncj 3. Anodic control protection: Increase in anodic overpotential jnaj 4. Mixed control protection: Increase in both anodic overpotential jnaj and cathodic overpotential jncj 5. Resistance control protection: Increase in resistance of corrosion cell R 7.1.3 EMF Control Protection The difference in potential between the anode and the cathode (EcKEa) is the EMF of the corrosion cell. It is also the degree of thermodynamic instability of the surface metal for the environment. In other words, the less the EMF, the lower the corrosion rate. By covering the surface of the active metal with a continuous layer of a more stable metal, the active metal surface becomes more thermodynamically stable. Dissolved oxygen and hydrogen ions,


412


that are the reactants in the cathodic reaction, are normal oxidizers found in natural environments. In the natural atmosphere, the single-potential of dissolved oxygen is nearly constant. Because of this, metals with more noble electrode potentials are used as coating materials. These include copper, silver, platinum, gold, and their alloys. A copper coating system provides excellent corrosion resistance under the condition that the defect-free continuous layer covers the surface of the iron substrate. In doing so, the EMF of the iron surface is decreased by the copper coating. The corrosion potential is changed from Ecorr of uncoated iron to Ecorr of copper by coating with copper. Under this condition, the iron corrodes at the low rate of icorr of copper. However, if the iron substrate is exposed to the environment, as the result of mechanical damage, the substrate is corroded predominantly at the rate of icorr of exposed copper by coupling iron and copper (galvanic corrosion). Organic coatings and paints are also able to provide EMF control protection. Surface conditions are converted to more stable states by coating with organic compounds. These coatings delay the generation of electromotive force, causing the corrosion of the substrate. How long an organic coating will be serviceable is dependent upon the durability of the coating and its adhesive ability on the base metal. The former is the stability of the coating layer as exposed to various environmental factors, and the latter is determined by the condition of the interface between the organic film and the substrate. EMF can also be decreased by the use of glass lining, porcelain enameling, and temporary coating with greases and oils. 7.1.4 Cathodic Control Protection Cathodic control protection protects the substrate by coating with a less noble metal, for which the slopes of the cathodic polarization curves are steep. The cathodic overpotential of the surface is increased by the coating; therefore, the corrosion potential becomes more negative than that of the substrate. Coating materials used for this purpose are zinc, aluminum, manganese, cadmium, and their alloys. The electrode potential of these metals are more negative than those of iron and steel. When exposed to the environment, these coatings act as sacrificial anodes for the iron and steel substrates. The protective abilities of coatings are as follows: 1. Original barrier action of coating layer 2. Secondary barrier action of corrosion product layer 3. Galvanic action of coating layer as sacrificial anode Barrier coatings 1 and 2 predominate as the protective ability even though a sacrificial metal coating is characterized by galvanic action.


Coatings

413

Initially, the substrate is protected against corrosion by the barrier action of the coating, followed by the barrier action of the corrosion product layer. Upon exposure to air, aluminum forms a chemically inert Al2O3 oxide film that is a rapidly forming self-healing film. Therefore, the passive film on aluminum, as well as the corrosion product layer, is a main barrier and leads to a resistant material in natural environments. On the other hand, the surface oxide film that forms on zinc is not as an effective barrier as the oxide film on aluminum. Upon exposure in the natural atmosphere, many corrosion cells are formed on the surface of a sacrificial metal coating, thereby, accelerating the corrosion rate. During this period, corrosion products are gradually formed and converted to a stable layer. This period may last for several months, after this period, the corrosion rate becomes constant. These corrosion products form the second barrier and are amorphous Al2O3 on aluminum, and Zn(OH)2 and basic zinc salts on zinc. ZnO, being electrically conductive, loosens the corrosion product layer and, therefore, does not contribute to formation of the barrier. When materials such as CO2, NaCl, and SOx are present, basic zinc salts are formed, for example, 2ZnCO3$ 3Zn(OH)2 in mild atmospheres, ZnCl2$6Zn(OH)2 in chloride atmospheres, and ZnSO4$4Zn(OH)2 in SOx atmospheres. How stable each basic zinc salt will be is dependent on the pH and anion concentration of the electrolyte on the zinc. Zinc carbonate forms an effective barrier on steel in mild atmospheres, whereas, basic zinc sulfate and chloride dissolve with decreasing pH of the electrolyte. The basic zinc sulfate is restricted under atmospheric conditions in its effort to act as a barrier since the pH value of rain in an SOx atmosphere is usually low, in the area of less than 5. In a chloride environment, the value of pH in the electrolyte is not as low as in the SOx atmosphere; therefore, a secondary barrier will form. However, in a severe chloride environment, the zinc coating layer will corrode in spite of the existence of basic zinc chloride on the surface. 7.1.4.1 Galvanic Action of Coating Layer Sacrificial metal coatings protect the substrate metal by means of galvanic action. When the base metal is exposed to the atmosphere as a result of mechanical damage or the like, the exposed portion of the base metal is polarized cathodically to the corrosion potential of the coating layer. As a result, little corrosion takes place on the exposed metal. A galvanic couple is formed between the exposed part of the base metal and the surrounding coating metal. Sacrificial metals are more negative in electrochemical potential than other metals such as iron or steel. Therefore, the sacrificial metal coating acts as a cathode. This type of reaction of sacrificial metal coatings is known as galvanic or cathodic protection. In addition, the defects are protected by a second barrier of corrosion products of the coating layer. Figure 7.4 schematically illustrates the galvanic action of a sacrificial metal coating.


414

Corrosion of Linings and Coatings O2

Electrolyte Zn2+ OH−

e

Steel

Zn

e

Zn(OH)2

Zn

Steel FIGURE 7.4 Schematic illustration of galvanic action of sacrificial metal coating.

7.1.5 Anodic Control Protection Noble metal coatings provide anodic control protection. They are usually used where corrosion protection and decorative appearance are required. Nickel, chromium, tin, lead, and their alloys are the coating metals that provide anodic protection. 7.1.5.1 Single Layer Coatings Single layer metal coatings provide corrosion protection as a result of the original barrier action of the noble metal. With the exception of lead, a second barrier of corrosion products is not formed. Noble metals do not provide cathodic protection to steel substances in natural atmospheres because the corrosion potential of the noble metal is more noble than that of the steel. Refer to Table 7.3.


Coatings

415 TABLE 7.3 Corrosion Potentials of Noble Metals Corrosion Potentials (V, SCE) pH

2.9

6.5

Chromium Nickel Tin Lead Steel

K0.119 K0.412 K0.486 K0.435 K0.636

K0.186 K0.430 K0.554 K0.637 K0.505

The service life of a single layer coating is affected by any discontinuity in the coating such as that caused by pores and cracks. For metals to form a protective barrier, the coating thickness must be greater than 30 mm to ensure absence of defects. The surface of a bright nickel coating will remain bright in a clean atmosphere but will change to a dull color when exposed in an SOx atmosphere. Chromium coatings are applied as a thin layer to maintain a bright, tarnish-free surface. Cracking of chromium coatings begins at a thickness of 0.5 mm after which a network of fine cracks is formed. For protection of steel in an SOx atmosphere, lead and its alloys (5–10% tin) coatings are employed. Pitting will occur in the lead coating at the time of initial exposure, but the pits are self-healing, and the lead surface is protected by the formation of insoluble lead sulfate. 7.1.5.2 Multilayer Coatings There are three types of nickel coatings: bright nickel, semibright, and dull. The difference is the quantity of sulfur contained in them as shown below: Bright nickel deposits Semibright nickel deposits Dull nickel deposits

O0.04% Sulfur !0.005% Sulfur !0.001% Sulfur

The corrosion potentials of the nickel deposits are dependent on the sulfur content. Figure 7.5 shows the effect of sulfur content on the corrosion potential of a nickel deposit. As the sulfur content increases, the corrosion potential of a nickel deposit becomes more negative. A bright nickel coating is less protective than a semibright or dull nickel coating. The difference in potential of bright nickel and semibright deposits is more than 50 mV. Use is made in the differences in the potential in the application of multilayer coatings. The more negative bright nickel deposits are used as sacrificial intermediate layers. When bright nickel is used as an intermediate


416


Corrosion potential of nickel, mV, SCE

−300

−350

Dull bright nickel coating

Semibright nickel coating

Bright nickel coating

−400

−450 0.001

0.01

0.1

1.0

Sulfur content wt% FIGURE 7.5 Effect of sulfur content on the corrosion potential of nickel deposit.

layer, the corrosion behavior is characterized by a sideways diversion. Pitting corrosion is diverted laterally when it reaches the more noble semibright deposit. Thus, the behavior of bright nickel prolongs the time for pitting penetration to reach the base metal. The most negative of all nickel deposits is trinickel. In the triplex layer coating system, a coating of trinickel approximately 1 mm thick, containing 0.1–0.25% sulfur is applied between bright nickel and semibright nickel deposits. The high sulfur nickel layer dissolves preferentially, even when pitting corrosion reaches the surface of the semibright deposit. Since the high sulfur layer reacts with the bright nickel layer, pitting corrosion does not penetrate the high sulfur nickel layer in the tunneling form. The application of a high sulfur nickel strike definitely improves the protective ability of a multistage nickel coating. 7.1.6 Resistance Control Protection Resistance control protection is achieved by using organic compounds, such as some paints, as coating materials. The coating layer delays the transit of ions to the substrate thereby, inhibiting the formation of corrosion cells. Figure 7.6 illustrates the principles of resistance control protection by an organic coating. The corrosion rate of iron is inhibited by the coating from icorr of uncoated iron to icorr of coated iron.


Coatings

417

Me

n+

Metallic film e

−

−

e

Substrate

FIGURE 7.6 Dissolution of substrate in coating metal defect.

7.2 Metallic Coatings Metallic coatings are applied to metal substrates for several purposes. Typical purposes include improved corrosion resistance, wear resistance, and appearance. Of primary concern is corrosion resistance. By providing a barrier between the substrate and the environment or by cathodically protecting the substrate, metallic coatings protect the substrate from corrosion. Coatings of chromium, copper, and nickel provide increased wear resistance and good corrosion resistance. However, these noble metals make the combination of the substrate (mostly steel or an aluminum alloy) with the protective layer sensitive to galvanically induced local corrosion. Nonnoble metallic layers such as zinc or cadmium provide good cathodic protection but show poor wear resistance. A coating of a corrosion resistant metal on a corrosion prone substrate can be formed by various methods. The choice of coating material and selection of an application method are determined by the end use. 7.2.1 Methods of Producing Coatings 7.2.1.1 Electroplating This is one of the most versatile methods. The metal to be coated is made the cathode in an electrolytic cell. A potential is applied between the cathode that the plating occurs on and the anode that may be the same metal or an inert material such as graphite. This method can be used for all metals that can be electrolytically reduced from the ionic state to the metallic state when present in an electrolyte. Aluminum, titanium, sodium, magnesium, and calcium cannot be electrodeposited from aqueous solution because the competing cathodic reaction, 2HCC2eKZH2, is strongly thermodynamically favored and takes place in preference to the reduction of the metal ion. These metals can be electrodeposited from conducting organic


418


solutions or molten salt solutions in which the HC ion concentration is negligible. Many alloys may be electrodeposited, including copper–zinc, copper–tin, lead–tin, cobalt–tin, nickel–cobalt, nickel–iron, and nickel–tin. The copper– zinc alloys are used to coat steel wire used in tire-cord. Lead–tin alloys are known as terneplate and have many corrosion resistant applications. The thickness of coating can be accurately controlled since the amount deposited is a function of the number of coulombs passed. 7.2.1.2 Electroless Plating This method is also known as chemical plating or immersion plating. It is based on the formation of metal coatings, resulting from chemical reduction of metal ions from solution. The surface that is to be coated must be catalytically active and remain catalytically active as the deposition proceeds in a solution that must contain a reducing agent. If the catalyst is a reduction product (metal), autocatalysis is ensured. In this case, it is possible to deposit a coating, in principle, of unlimited thickness. The advantages of electroless plating are: 1. Deposits have fewer pinholes. 2. Electric power supply is not required. 3. Nonconductive materials are metallized. 4. A functional layer is deposited. 5. A uniform layer is deposited, even on complex parts. 6. The equipment for electroless plating is simple. Electroless plating is limited by the fact that: 1. It is more expensive than electroplating because the reducing agents cost more than an equivalent amount of electricity. 2. It is less intensive because the metal deposition rate is limited by metal ion reduction in the bulk of the solution. Copper, silver, cobalt, and palladium are the most commonly plated metals using this process. The silvering of mirrors falls into this category. Hypophosphite, amine boranes, formaldehyde, borohydride, and hydrozine are typical reducing agents. Deposits of nickel formed with hypophosphite as a reducing agent contain phosphorus. This alloying constituent determines many of the properties. Table 7.4 shows coatings obtained by electroless plating. 7.2.1.3 Electrophoretic Deposition Finely divided materials suspended in an electrolyte develop a charge as a result of asymmetry in the charge distribution caused by the selective


Coatings

419

TABLE 7.4 Coatings Obtained by Electroless Plating Reducing Agent Metal Ni Co Fe Cu Ag Au Pd Rh Ru Pt Sn Pb

H2 POL 4

N2H2

CH2O

Ni–P Co–P

Ni Co

Co

Cu

Cu Ag Au Pd Rh

Pd–P

Pt

Cu Ag Au Pd Ru Pt Pb

BHL 4

RBH3

Ni–B Co–B Fe–B Cu Ag Au Pd–B

Ni–B Co–B Cu Ag Au Pd–B

Me ions

Cu Ag

Others

Ag Au Rh

Sn

Pt

adsorption of one of the constituent ions. When the substrate metal is immersed in the electrolyte, and a potential is applied, a coating will be formed. If the particles have a negative charge, they will be deposited on the anode, and if they have a positive charge, they will be deposited on the cathode. Commercial applications of this method in the case of metals is limited. 7.2.1.4 Cathodic Sputtering This method is carried out under a partial vacuum. The substrate to be coated is attached to the anode. Argon, or a similar inert gas, is admitted at low pressure. A discharge is initiated, and the positively charged gas ions are attracted to the cathode. Atoms are dislodged from the cathode as the gas ions collide with the cathode. These atoms are attracted to the anode and coat the substrate. This method can be used for nonconducting as well as conducting materials. The major disadvantages are the heating of the substrate and low deposition rates. Some of the most commonly used metals deposited by sputtering are aluminum, copper, chromium, gold, molybdenum, nickel, platinum, silver, tantalum, titanium, tungsten, vanadium, and zirconium. Sputtered coatings are used for a wide variety of applications. Some examples are: 1. Metals and alloys are used as conductors, contacts, and resistors and in other components such as capacitors. 2. Some high performance magnetic data storage media are deposited via sputtering.


420


3. Thin metal and dielectric coatings are used to construct mirrors, antireflection coatings, light valves, laser optics, and lens coatings. 4. Hard coatings such as titanium carbide, nitride, and carbon produce wear-resistant coatings for cutting tools. 5. Thin film coatings can be used to provide high temperature environmental corrosion resistance for aerospace and engine parts, gas barrier layers, and lightweight battery components. 6. Titanium nitride is deposited on watch bands and jewelry as a hard gold colored coating. 7.2.1.5 Diffusion Coating This method requires a preliminary step followed by thermal treatment and diffusion of the coating metal into the substrate. A commercial material known as galvannealed steel is made by coating steel with zinc followed by heat treatment and the formation of an iron–zinc intermetallic coating by diffusion. 7.2.1.6 Flame Spraying The coating metal is melted and kept in the molten condition until it strikes the substrate to be coated. Aluminum and zinc are applied in this manner. Flame sprayed aluminum has a lower density than pure aluminum because of voids in the coating. 7.2.1.7 Plasma Spraying This method is similar to flame spraying except that forms of heating other than a flame are used. 7.2.1.8 Hot Dipping Zinc coatings are applied to steel sheets by immersion of the steel in a molten bath of zinc to form galvanized steel. A small amount of aluminum is added to the bath to establish a good bond at the zinc–steel interface. The thickness of the zinc coating is controlled by rigid control of the galvanizing bath temperature, the speed of passage through the bath, the temperature of the steel sheet before it enters the bath, and the use of air jets that exert a wiping action as the steel sheet exits the bath. 7.2.1.9 Vacuum and Vapor Deposition This method is used primarily for the formation of metallic coatings on nonconductive substrates. Common deposited coatings using this method include aluminum coatings on plastics and rhodium coatings on mirrors.


Coatings

421

7.2.1.10 Gas Plating Some metal compounds can be decomposed by heat to form the metal. Typical examples are metal carbonyls, metal halides, and metal methyl compounds. 7.2.1.11 Fusion Bonding Coatings of low melting metals such as tin, lead, zinc, and aluminum may be applied by cementing the metal as a powder on the substrate then heating the substrate to a temperature above the melting point of the coating metal. 7.2.1.12 Explosion Bonding This method produces a bond between two metals by the exertion of a strong force that compresses the two metals sufficiently to develop a strong interfacial interaction. 7.2.1.13 Metal Cladding The most common method is roll bonding that produces full-sized sheets of clad (coated) material. The bond formed is partly mechanical and partly metallurgical; consequently, metallurgically incompatible materials cannot be produced.

7.3 Noble Coatings Because of the high corrosion resistance of the noble metals, these materials are used where a high degree of corrosion resistance and decorative appearance are requirements. They find application in domestic appliances, window frames, bicycles. motorbikes, parts for car bodies, furniture, tools, flanges, hydraulic cylinders, shock absorbers in cars, and parts of equipment for the chemical and food processing industries. Noble metal coatings protect substrates from corrosion by means of anodic control or EMF control. Coating metals that provide protection by means of anodic control include nickel, chromium, tin, lead, and their alloys. They can protect the substrate metal as a result of their resistance to corrosion insofar as they form a well-adhering and nonporous barrier layer. However, when the coating is damaged, galvanically induced corrosion will lead to severe attack. This corrosion process is extremely fast for coated systems because of the high current density in the defect as a result of the large ratio between the surface areas of the cathodic outer surface and the anodic defect, as shown in Figure 7.7. To compensate for these defects in the coating, multilayer coating systems have been developed. The corrosion resistance of a single layer noble metal coating results from the original barrier action of the noble metal, the surface of the noble metal being


422


Ec

O

2

+

2H

2O

+4 e

Ecorr of iron

H−

Ricorr of coated iron

Electrode potential

4O

2+

Fe

+

2e

Fe

Ea icorr of

coated iron

icorr of

uncoated iron

Log current density FIGURE 7.7 Resistance control protection. (From I. Suzuki. 1989. Corrosion Resistant Coatings Technology, New York: Marcel Dekker.)

passivated. With the exception of lead, a secondary barrier of corrosion products is not formed. Noble metals do not provide cathodic protection for the steel substrate because their corrosion potential is more noble than those of iron and steel in a natural environment. Refer to Table 7.5. In multilayer coating systems, a small difference in potential between coating layers results in galvanic action in coating layers. Noble coating metals that provide corrosion protection by means of EMF control include copper, silver, platinum, gold, and their alloys. The standard single potentials of these metals are more noble than those of hydrogen (refer to Table 7.6). Therefore, the oxidizer in corrosion cells formed on these metals in a natural environment, containing no other particular oxidizers, TABLE 7.5 Corrosion Potential of Noble Metals Corrosion Potentials (V, SCE) pH

2.9

6.5

Chromium Nickel Tin Lead

K0.119 K0.412 K0.486 K0.435

K0.186 K0.430 K0.554 K0.637

Steel

K0.636

K0.505


Coatings

423 TABLE 7.6 Standard Single Potentials, E8 (V, SHE, 258C) Inert Electrode C

H2/H Cu/Cu2C Cu/CuC Ag/AgC Pt/Pt2C Au/Au3C Au/AuC

E8 G0 C0.34 C0.52 C0.799 C1.2 C1.42 C1.7

is dissolved oxygen. Consequently, the electromotive force that causes corrosion is so small that coating with noble metals is an effective means of providing corrosion protection. With the exception of copper, the other members of this group are precious metal and are primarily used for electrical conduction and decorative appearance. 7.3.1 Nickel Coatings There are three types of nickel coatings: bright, semibright, and dull bright. The difference between the coatings is in the quantity of sulfur contained in them as shown below: Bright nickel deposits Semibright nickel deposits Dull bright nickel deposits

O0.04% Sulfur !0.005% Sulfur !0.001% Sulfur

The corrosion potentials of the nickel deposits are dependent on the sulfur content. Figure 7.8 shows the effect of sulfur content on the corrosion potential of a nickel deposit. A single layer nickel coating must be greater than 30 mm to ensure absence of defects. As the sulfur content increases, the corrosion potential of a nickel deposit becomes more negative. A bright nickel coating is less protective than a semi-bright or dull nickel coating. The difference in the potential of bright nickel and semibright nickel deposits is more than 50 mV. Use is made of the differences in the potential in the application of multilayer coatings. The more negative bright nickel deposits are used as sacrificial intermediate layers. When bright nickel is used as an intermediate layer, the corrosion behavior is characterized by a sideways diversion. Pitting corrosion is laterally diverted when it reaches the more noble semibright nickel deposit. Thus, the corrosion behavior of bright nickel prolongs the time for pitting penetration to reach the base metal.


424


−350

Bright nickel coating

Semibright nickel coating

Dull nickel coating

Corrosion potential of nickel mV, SCE

−300

−400

−450 0.001

0.01

0.1

1.0

Sulfur content, wt% FIGURE 7.8 Effect of sulfur content on corrosion protection of nickel.

The most negative of all nickel deposits is trinickel. In the triplex layer coating system, a coating of trinickel approximately 1 mm thick, containing 0.1–0.25% sulfur, is applied between bright nickel and semibright nickel deposits. The high sulfur nickel layer dissolves preferentially, even when pitting corrosion reaches the surface of the semibright nickel deposit. Because the high sulfur layer reacts with the bright nickel layer, pitting corrosion does not penetrate the high sulfur nickel layer in the tunneling form. The application of a high sulfur nickel strike definitely improves the protective ability of a multilayer nickel coating. In the duplex nickel coating system, the thickness ratio of semibright nickel deposit to bright nickel deposit is nominally 3:1, and a thickness of 20–25 mm is required to provide high corrosion resistance. The properties required for a semibright nickel deposit are as follows: 1. The deposit contains little sulfur. 2. Internal stress must be slight. 3. Surface appearance is semibright and extremely level. For a trinickel (high sulfur) strike, the following properties are required: 1. The deposit contains a stable 0.1–0.25% sulfur. 2. The deposit provides good adhesion for semibright nickel deposits. Nickel coatings can be applied by electrodeposition or electrolessly from an aqueous solution without the use of an externally applied current.


Coatings

425

Depending on the production facilities and the electrolyte composition, electrodeposited nickel can be relatively hard (120–400 HV). Despite competition from hard chromium and electroless nickel, electrodeposited nickel is still being used as an engineering coating because of its relatively low price. Some of its properties are: 1. Good general corrosion resistance 2. Good protection from fretting corrosion 3. Good machineability 4. The ability of layers of 50–75 mm to prevent scaling at high temperatures 5. Mechanical properties, including the internal stress and hardness, that are variable and that can be fixed by selecting the manufacturing parameters 6. Excellent combination with chromium layers 7. A certain porosity 8. A tendency for layer thicknesses below 10–20 mm on steel to give corrosion spots because of porosity The electrodeposition can be either directly on steel or over an intermediate coating of copper. Copper is used as an underlayment to facilitate buffing, because it is softer than steel, and to increase the required coating thickness with a material less expensive than nickel. The most popular electroless nickel plating process is the one where hypophosphite is used as the reducer. Autocatalytic nickel ion reduction by hypophosphite takes place in both acid and alkaline solutions. In a stable solution with a high coating quality, the deposition rate may be as high as 20–25 mm/h. However, a relatively high temperature of 1948F/908C is required. Because hydrogen ions are formed in the reduction reaction, K Ni2C C 2H2 POK 2 C 2H2 O/ Ni C 2H2 C 2H ;

a high buffering capacity of the solution is necessary to ensure a steady state process. For this reason, acetate, citrate, propionate, glycolate, lactate, or aminoacetate is added to the solutions. These substances along with buffering may form complexes with nickel ions. Binding Ni2C ions into a complex is required in alkaline solutions (here ammonia and pyrophosphate may be added in addition to citrate and amino-acetate). In addition, such binding is desirable in acid solutions because free nickel ions form a compound with the reaction product (phosphate) that precipitates and prevents further use of the solution. When hypophosphite is used as the reducing agent, phosphorus will be present in the coating. Its amount (in the range of 2–15 mass percent) depends on pH, buffering capacity, ligands, and other parameters of electroless solutions.


426


Borohydride and its derivatives may also be used as reducing agents. When borohydride is used in the reduction, temperatures of 1408F/608C to 1948F/908C are required. The use of dimethylaminoborane (DMAB) enables the deposition of Ni–B coatings with a small amount of boron (0.5–1.0 mass percent) at temperatures in the range of 868F/308C to 1048F/608C. Neutral and alkaline solutions may be used. Depending upon exposure conditions, certain minimum coating thicknesses to control porosity are recommended for the coating to maintain its appearance and have a satisfactory life: Indoor exposures Outdoor exposures Chemical industry

0.3–0.5 mil (0.008–0.013 mm) 0.5–1.5 mil (0.013–0.04 mm) 1–10 mil (0.025–0.25 mm)

For applications near the seacoast, thicknesses in the range of 1.5 mil (0.04 mm) should be considered. This also applies to automobile bumpers and applications in general industrial atmospheres. Nickel is sensitive to attack by industrial atmospheres and forms a film of basic nickel sulfate that causes the surface to “fog” or lose its brightness. To overcome this fogging, a thin coating of chromium (0.01–0.03 mil/0.003– 0.0007 mm) is electrodeposited over the nickel. This finish is applied to all materials for which continued brightness is desired. Single-layer coatings of nickel exhibit less corrosion resistance than multilayer coatings because of their discontinuities. The electroless plating process produces a coating with fewer discontinuous deposits. Therefore, the single layer deposited by electroless plating provides more corrosion resistance than does an electroplated single layer. Most electroless plated nickel deposits contain phosphorus that enhances corrosion resistance. In the same manner, an electroplated nickel deposit containing phosphorus will also be more protective. 7.3.2 Satin-Finish Nickel Coating A satin-finish nickel coating consists of nonconductive materials such as aluminum oxide, kaolin, and quartz that are codeposited with chromium on the nickel deposit. Some particles are exposed on the surface of the chromium deposit, so the deposit has a rough surface. Because the reflectance of the deposit is decreased to less than half of that of a level surface, the surface appearance looks like satin. A satin finish nickel coating provides good corrosion resistance because of the discontinuity of the top coat of chromium. 7.3.3 Nickel–Iron Alloy Coating To reduce production costs of bright nickel, the nickel–iron alloy coating was developed. The nickel–iron alloy deposits full brightness, high leveling, and excellent ductility and good reception for chromium.


Coatings

427

This coating has the disadvantage of forming red rust when immersed in water; consequently, nickel–iron alloy coating is suitable for use in mild atmospheres only. Typical applications include kitchenware and tubular furniture. 7.3.4 Chromium Coatings In the northern parts of the United States, immediately after World War II, it was not unusual for the chromium plated bumpers on the most expensive cars to show severe signs of rust within a few months of winter exposure. This was partially the result of trying to extend the short supply of strategic metals by economizing on the amount used. However, the more basic reason was the lack of sufficient knowledge of the corrosion process in order to control the attack by the atmosphere. Consequently, an aggressive industrial program was undertaken to obtain a better understanding of the corrosion process and ways to control it. Chromium-plated parts on automobiles consist of steel substrates with an intermediate layer of nickel, or in some cases, layered deposits of copper and nickel. The thin chromium deposit provides bright appearance and stain free surface while the nickel layer provides the corrosion protection to the steel substrate. With this system, it is essential that the nickel completely cover the steel substrate because the iron will be the anode and nickel the cathode. Any breaks or pores in the coating will result in the condition shown in Figure 7.9. This figure illustrates the reason for the corrosion of chrome trim on automobiles after World War II. The corrosion problem was made worse by the fact that addition agents used in the plating bath resulted in a bright deposit. Bright deposits contain sulfur that makes the nickel more active from a corrosion standpoint. From a corrosion standpoint, this is discouraging. However, it occurred to the investigators that this apparent disadvantage of bright nickel could be put to good use. Cathodic reaction takes place on chromium or nickel −

H2O + 12O2 + 2e

2OH−

Rust corrosion product

Chromium deposit Nickel deposit Steel substrate Anodic reaction takes place on iron exposed through coating −

Fe − 2e

Fe++

FIGURE 7.9 Corrosion of steel at breaks in a nickel/chromium coating when exposed to the atmosphere.


428

Corrosion of Linings and Coatings Corrosion contained to nickel layer containing sulfur

Microcracked chromium Bright nickel containing sulfur Sulfur-free nickel Steel substrate

FIGURE 7.10 Duplex nickel electrode deposit to prevent corrosion of steel substrate.

To solve this problem, a duplex nickel coating was developed as shown in Figure 7.10. An initial layer of sulfur-free nickel is applied to the steel substrate, followed by an inner layer of a bright nickel containing sulfur, with an outer layer of microcracked chromium. Any corrosion that takes place is limited to the bright nickel layer containing sulfur. The corrosion laterally spreads between the chromium and sulfur free nickel deposits because the outer members of this sandwich (chromium and sulfur free nickel) are cathodic to the sulfur containing nickel. A potential problem that could result from this system of corrosion control would be the undermining of the chromium and the possibility that the brittle chromium deposits could flake off the surface. This potential problem was prevented by the development of a microcracked or microporous chromium coating. These coatings contain microcracks or micropores that do not detract from the bright appearance of the chromium. They are uniformly formed over the exterior of the plated material and serve to distribute the corrosion process over the entire surface. The result has been to extend the life of chromium-plated steel exposed to outdoor atmospheric conditions. Microcracked chromium coatings are produced by first depositing a high stress nickel strike on a sulfur free nickel layer and then a decorative chromium deposit. The uniform crack network results from the interaction of the thin chromium layer and the high stress nickel deposit. The result is a mirror surface as well as a decorative chromium coating. Microporous chromium coatings are produced by first electroplating a bright nickel layer containing suspended nonconductive fine particles. Over this, a chromium layer is deposited which results in a mirror finish. As the chromium thickness increases the number of pores decrease. For a chromium deposit of 0.25 mm thickness, a porosity of more than 10,000 pores/cm2 are required. A porosity of 40,000 pores/cm2 provides the best corrosion resistance.


Coatings

429

Hard (engineering) chromium layers are also deposited directly on a variety of metals. The purpose in applying these layers is to obtain wear resistant surfaces with a high hardness or to restore original dimensions to a workpiece. In addition, the excellent corrosion resistance resulting from these layers make them suitable for outdoor applications. Thick chromium deposits have high residual internal stress and may be brittle because of the electrodeposition process that hydrogen can be incorporated in the deposited layer. Cracks result during plating when the stress exceeds the tensile stress of the chromium. As plating continues, some cracks are filled. This led to the development of controlled cracking patterns that produce wet-table porous surfaces that can spread oil that is important for engine cylinders, liners, etc. Some of the properties of engineering chromium layers are: 1. Excellent corrosion resistance 2. Wear resistance 3. Hardness up to 950 HV 4. Controlled porosity is possible 7.3.5 Tin Coatings (Tinplate) Tinplate is mainly produced by the electroplating process. Alkaline and acid baths are used in the production line. The acid baths are classified as either ferrostan or halogen baths. A thermal treatment above the melting point of tin follows the electrolytic deposition. The intermetallic compound FeSn2 forms at the interface between the iron and tin during this thermal processing. The corrosion behavior of the tinplate is determined by the quality of the FeSn2 formed, particularly when the amount of the free tin is small. The best performing tinplate is one where the FeSn2 uniformly covers the steel so that the area of iron exposed is very small in case the tin should dissolve. Good coverage requires good and uniform nucleation of FeSn2. Many nuclei form when electrodeposition of tin is carried out from the alkaline stannate bath. Compared to either iron or tin, FeSn2 is chemically inert in all but the strongest oxidizing environments. Most of the tinplate (tin coating on steel) produced is used for the manufacture of food containers (tin cans). The nontoxic nature of tin salts makes tin an ideal material for the handling of foods and beverages. An inspection of the galvanic series will indicate that tin is more noble than steel and, consequently, the steel would corrode at the base of the pores. On the outside of a tinned container this is what happens—the tin is cathodic to the steel. However, on the inside of the container there is a reversal of polarity because of the complexing of the stannous ions by many food products. This greatly reduces the activity of the stannous ions, resulting in a change in the potential of tin in the active direction.


430

Corrosion of Linings and Coatings Steel base

Tinplate (sacrificial)

Electrolyte

Outside of container

Electrolyte

Tinplate (noble)

Inside of container

FIGURE 7.11 Tin acting as both a noble and sacrificial coating.

This change in polarity is absolutely necessary because most tin coatings are thin and, therefore, porous. To avoid perforation of the can, the tin must act as a sacrificial coating. Figure 7.11 illustrates this reversal of activity between the outside and inside of the can. The environment inside a hermetically sealed can varies depending upon the contents that include general foods, beverages, oils, aerosol products, liquid gases, etc. For example, pH values vary for different contents as shown below: Acidic beverage Beer and wine Meat, fish, marine products, and vegetables Fruit juices, fruit products Nonfood products

2.4–4.5 3.5–4.5 4.1–7.4 3.1–4.3 1.2–1.5

The cans’ interiors are subject to general corrosion, localized corrosion, and discoloring. The coating system for tinplate consists of tin oxide, metallic tin, and alloy. The dissolution of the tin layer in acid fruit products is caused by acids such as citric acid. In acid fruit products, the potential reversal occurs between the tin layer and the steel substrate as shown in Figure 7.12. The potential reversal of a tin layer for steel substrate occurs at a pH range !3.8 in a citric acid solution. This phenomenon results from the potential shift of the tin layer to a more negative direction. Namely, the activity of the stannous ion, Sn2C, is reduced by the formation of soluble tin complexes, and, thereby, the corrosion potential of the tin layer becomes


431

Potential difference Esn − Efe + mV

Coatings

40 20 0 −20 −40

0

1

2

4

3

5

6

7

pH FIGURE 7.12 Potential reversal in tinplate.

more negative than that of steel. Thus, the tin layer acts as a sacrificial anode for steel so that the thickness and density of the pores in the tin layer are important factors affecting the service life of the coating. A thicker tin layer prolongs the service life of a tin can. The function of the alloy layer (FeSn) is to reduce the active area of steel by covering it since it is inert in acid fruit products. When some parts of the steel substrate are exposed, the corrosion of the tin layer is accelerated by galvanic coupling with the steel. The corrosion potential of the alloy layer is between that of the tin layer and that of the steel. A less defective layer exhibits potential closer to that of the tin layer. Therefore, the covering with alloy layer is important to decrease the dissolution of the tin layer. In carbonated beverages, the potential reversal does not take place; therefore, the steel preferentially dissolves at the defects in the tin layer. Under such conditions, pitting corrosion sometimes results in perforation. Consequently, except for fruit cans, almost all tinplate cans are lacquered. When tinplate is to be used for structural purposes such as roofs, an alloy of 12–25 parts of tin to 88–75 parts of lead is frequently used. This is called terneplate. It is less expensive and more resistant to the weather than a pure tin coating. Terneplate is used for fuel tanks of automobiles and is also used in the manufacture of fuel lines, brake lines, and radiators in automobiles. 7.3.6 Lead Coatings Coatings of lead and its alloy (5–10% Sn) protect steel substrate especially in industrial areas having an SOx atmosphere. At the time of initial exposure, pitting occurs on the lead surface; however, the pits are selfhealed and then the lead surface is protected by the formation of insoluble lead sulfate. Little protection is provided by these coatings when in contact with the soil.


432


Lead coatings are usually applied by either hot dipping or by electrodeposition. When the coating is to be applied by hot dipping, a small percentage of tin is added to improve the adhesion to the steel plate. If 25% or more of tin is added, the resulting coating is termed terneplate. Caution: Do not use lead coatings where they will come into contact with drinking water or food products. Lead salts can be formed that are poisonous. 7.3.7 Terneplate Terneplate is a tin-lead alloy coated sheet steel and is produced either by hot dipping or electrodeposition. The hot dipping process with a chloride flux is used to produce most terneplates. The coating layer, whose electrode potential is more noble than that of the steel substrate, contains 8–16% Sn. Since the electrode potential of the coating layer is more noble than the steel substrate, it is necessary to build a uniform and dense alloy layer (FeSn2) in order to form a pinhole free deposit. Terneplate exhibits excellent corrosion resistance, especially under wet conditions, excellent weldability and formability, with only small amounts of corrosion products forming on the surface. A thin nickel deposit can be applied as an undercoat for the terne layer. Nickel reacts rapidly with the tinlead alloy to form a nickel–tin alloy layer. This alloy layer provides good corrosion resistance and inhibits localized corrosion. The main application for terneplate is in the production of fuel tanks for automobiles. 7.3.8 Gold Coatings Gold electrodeposits are primarily used to coat copper in electronic applications to protect the copper connectors and other copper components from corrosion. It is desirable to obtain the corrosion protection with the minimum thickness of gold because of the cost of the gold. As the thickness of the electrodeposit is decreased, there is a tendency for the deposit to provide inadequate coverage of the copper. For this reason, it is necessary that there be a means whereby the coverage of the copper can be determined. Such a test, using corrosion principles as a guide, has been developed. In a 0.1 M NH4Cl solution, gold serves as the cathode and copper serves as the anode. At a high cathode/anode surface area fraction, the corrosion potential is linearly related to the area fraction of copper exposed, as shown in Figure 7.13. By measuring the corrosion potential of the gold plated copper in a 0.1 M NH4Cl solution, the area fraction of copper exposed is determined. Gold coatings can also be deposited by means of electroless plating. Borohydride or DMAB are used as reducers with a stable gold cyanide complex. Thin gold coatings may be deposited on plastics by an aerosol spray method using gold complexes with amines and hydrazine as a reducer. A relatively thick coat may be obtained.


Coatings

433

10−3

Area fraction copper

10−4

10−5

Bath: 0.1M NH4 Cl

10−6

10−7

40

20

0

−20

−40

−60

−80

−100

Corrosion potential, mV(vs SCE) FIGURE 7.13 Data showing that the fractional exposed area of copper in copper/gold system is linearly related to the corrosion potential at low-exposed copper areas.

7.3.9 Copper Coatings Even though copper is soft, it has many engineering applications in addition to its decorative function. One such application is the corrosion protection of steel. It can be used as an alternative to nickel to prevent fretting and scaling corrosion. Copper can be electrochemically deposited from various aqueous solutions. The properties of the deposit will depend on the chosen bath and the applied procedures. The hardness of the layers varies from 40 to 160 HV. Since copper is very noble, it causes extreme galvanically induced local corrosion of steel and aluminum substrates. Because of this, extreme care must be taken to produce well-adhering nonporous layers. The corrosion protection provided by a copper coating is twofold, consisting of an original barrier action of the coating layer and a secondary barrier action of corrosion products. The low EMF of copper is responsible


434


for the formation of the original barrier action. The electrochemical reactions in the corrosion cells on copper are as follows: Cu/ CuC C e

Anodic reaction :

Cu/ Cu2C C 2e Cathodic reaction :

O2 C H2 O/ 4e C 4OHK

Chloride ions in a natural environment stabilize cuprous ions. Cupric ions are more stable. Since the EMF of corrosion on copper is less than that on iron, the reactivity of a steel surface is decreased by coating it with copper. Over a period of time, corrosion products gradually build up a secondary layer against corrosion. Initially, a cuprous oxide layer is formed, followed by the copper surface covered with basic copper salts. Pollutants in the atmosphere determine the formation of basic copper salts as follows: Mild atmosphere SOx atmosphere Chloride atmosphere

Malachite CuCO3:Cu(OH)2 Brochanite CuSO4:3Cu(OH)2 Atacamite CuCl2:3Cu(OH)2

In most coastal areas, the amount of sulfates in the atmosphere exceeds the amount of chlorides. As a layer of copper salt grows on the surface of the corrosion product layer, the protective ability of the corrosion layer is increased. As the exposure time increases, the average corrosion rate of copper gradually decreases. After twenty years, the corrosion rate of copper is reduced to half the value of the first year as a result of the secondary barrier of corrosion products. The initial corrosion rate of a copper coating is dependent on atmospheric conditions such as time of wetness and type and amount of pollutants. Time of wetness is the most important factor affecting the corrosion rate of copper. The corrosion rate of copper usually obeys parabolic law: M2 Z kt; where MZmass increase kZa constant tZexposure time Accordingly, the average corrosion rate decreases with increased exposure time, that means the surface of the copper is covered with basic salts by degrees, and thereafter, the corrosion rate approaches a constant value. Copson6 conducted twenty year exposure tests and found the average corrosion rate of copper to be as follows: 0.0034 mil/year in dry rural atmospheres 0.143 mil/year in rural atmospheres


Coatings

435

0.0476–0.515 mil/year in industrial atmospheres 0.0198–0.0562 mil/year in marine atmospheres Until the base metal is exposed, the corrosion process of a copper coated layer is similar to that of copper plate. Galvanic corrosion of copper coated steel is induced when the steel substrate is exposed. However, in the case of copper coated stainless steel, the occurrence of galvanic action is dependent on the composition of the stainless steel. In chloride atmospheres galvanic pitting takes place at the pores in copper layers and galvanic tunneling at cut edges on types 409 and 430 stainless steels, whereas, in SOx atmospheres uniform corrosion takes place on the copper coating. Copper coatings are used both for decorative and for corrosion protection from the atmosphere. Copper coated steels are used as roofs, flashings, leaders, gutters, and architectural trim. Copper undercoats also improve the corrosion resistance of multilayered coatings, specifically in the plating of nickel and chromium.

7.4 Nonnoble Coatings Nonnoble metals protect the substrate by means of cathodic control. Cathodic overpotential of the surface is increased by coating which makes the corrosion potential more negative than that of the substrate. The coating metals used for cathodic control protection are zinc, aluminum, manganese, and cadmium-and their alloys, of which the electrode potentials are more negative than those of iron and steel. Consequently, the coating layers of these metals act as sacrificial anodes for iron and steel substrates, when the substrates are exposed to the atmospheres. The coating layer provides cathodic protection for the substrate by galvanic action. These metals are called sacrificial metals. The electrical conductivity of the electrolyte, the temperature, and the surface condition determines the galvanic action of the sacrificial metal coating. An increase in the cathodic overpotential is responsible for the corrosion resistance of the coating layer. Figure 7.14 shows the principle of cathodic control protection by a sacrificial metal coating. The corrosion rate of zinc coated iron icorr of zinc coating becomes lower than that of uncoated iron icorr of zinc uncoated iron because the cathodic overpotential of the surface is increased by zinc coating and the exchange current density of dissolved oxygen on zinc ioc on zinc is lower than that on iron ioc on iron. If a small part of iron is exposed to the atmosphere, the electrode potential of the exposed iron is equal to the corrosion potential of zinc Ecorr of zinc coating because the exposed iron is polarized cathodically by the surrounding zinc so that little corrosion occurs on the exposed iron


436


O 2 + O2

2H 2O

+

+

O 2H 2

4e 4O

H−

+ 4e

Electrode potential

+

2e

Fe

− H 4O

Ecorr

2+ Fe

of iron

2+ + Zn

2e

Zn

Ecorr of zinc

ioc on zinc

ioc on iron

icorr of exposed iron

icorr of zinc coating

icorr of uncoated iron

Log current density

FIGURE 7.14 Cathodic control protection.

icorr of exposed iron. Zinc ions predominately dissolved from the zinc coating form the surrounding barrier of corrosion products at the defect and, thereby, protect the exposed iron. Sacrificial metal coatings protect iron and steel by two or three protective abilities such as: 1. Original barrier action of coating layer 2. Secondary barrier action of corrosion product layer 3. Galvanic action of coating layer The surface oxide film and the electrochemical properties based on the metallography of the coating metal provide the original barrier action.


Coatings

437

˚ thick forms on aluminum. An air formed film of Al2O3 approximately 25 A This film is chemically inert, and its rapid formation of oxide film by a selfhealing ability leads to satisfactory performance in natural environments. Zinc, however, does not produce a surface oxide film that is as effective a barrier as the oxide film on aluminum. The original barriers of zinc and zinc alloy coatings result from electrochemical properties based on the structure of the coating layer. Nonuniformity of the surface condition generally induces the formation of a corrosion cell. Such nonuniformity results from defects in the surface oxide film, localized distribution of elements, and the difference in crystal face or phase. These nonuniformities of surface cause the potential difference between portions of the surface, thereby, promoting the formation of a corrosion cell. Many corrosion cells are formed on the surface, accelerating the corrosion rate, as a sacrificial metal and its alloy-coated materials are exposed in the natural atmosphere. During this time, corrosion products are gradually formed and converted to a stable layer after a few months of exposure. Typical corrosion products formed are shown in Table 7.7. Once the stable layer has been formed, the corrosion rate becomes constant. This secondary barrier of corrosion protection continuously regenerates over a long period of time. In most cases, the service life of a sacrificial metal coating depends on the secondary barrier action of the corrosion product layer. Sacrificial metal coatings are characterized by their galvanic action. Exposure of the base metal, as a result of mechanical damage, polarizes the base metal cathodically to the corrosion potential of the coating layer, as shown in Figure 7.14 so that little corrosion takes place on the exposed base metal. A galvanic couple is formed between the exposed part of the base metal and the surrounding coating metal. Because sacrificial metals are more negative in electrochemical potential than iron or steel, a sacrificial metal acts as an anode and the exposed base metal behaves as a cathode. Table 7.8 shows the corrosion potentials of sacrificial metals and steel in a 3% NaCl solution. Consequently, the dissolution of the coating layer around the defect is accelerated, and the exposed part of base metal is protected against corrosion. Figure 7.15 shows a schematic illustration of the galvanic action of a sacrificial metal coating. TABLE 7.7 Corrosion Products Formed on Various Sacrificial Metal Coatings Metal Al Zn Mn Cd

Corrosion Product Al2O3, bAl2O3$3H2O, aAlOOH, Al(OH)3, amorphous Al2O3 ZnO, Zn(OH)2, 2ZnCO3$3Zn(OH)2, ZnSO4$4Zn(OH)2, ZhCl2$4Zn(OH)2, ZnCl2$6Zn(OH)2 gOMn2O3, MnCO3, g-MnnOOH CdO, CdOH2, 2CdCO3$3Cd(OH)2


438

Corrosion of Linings and Coatings TABLE 7.8 Corrosion Potentials of Sacrificial Metals in a 3% NaCl Solution Metal

Corrosion Potential (V, SCE)

Mn Zn Al Cd

K1.50 K1.03 K0.79 K0.70

Steel

K0.61

The loss of metal coating resulting from corrosion determines the service life of the coating. The degree of loss is dependent on the time of wetness on the metal surface and the type of concentration of pollutants in the atmosphere. Table 7.9 shows the average corrosion losses of zinc, aluminum, and 55% Al–Zn coatings in various locations and atmospheres. The losses were calculated from the mean values of time of wetness and the average corrosion rate during wet duration. The time of wetness of walls is 40% of that of roofs. Coating metals and coating thicknesses can be decided from Table 7.9 since the corrosion losses of zinc, aluminum, and Al–Zn alloy are proportional to exposure time. As can be seen from the table, a G90 sheet that has a 1 mil zinc coating, cannot be used for a roof having a durability of ten years in any atmosphere except in a rural area. Were this sheet to be used in an urban, marine, or industrial atmosphere, it would have to be painted for protection.

O2

Electrolyte

Zn OH− e

Steel

Zn (OH)2 Steel FIGURE 7.15 Schematic illustration of galvanic action of sacrificial metal coating.


0.42 1.48 1.40 1.59 0.59 1.97 1.40 2.12 0.74 2.47 1.75 2.65 2.06

Urban Industrial Severe industrial Rural Urban Industrial Severe industrial Severe industrial

Root

Rural Urban Industrial Severe industrial Rural

Atmosphere

Zinc

0.79 0.56 0.85 0.23 0.99 0.70 1.06 0.82

0.17 0.59 0.56 0.64 0.24

Wall

0.18

0.10

0.25 0.46

0.10

0.25

0.08

0.08

0.20 0.20

0.06

0.25

Wall 0.06

55% AlZn 0.15

Root

Average Corrosion Loss (mila/10 years)

1 milZ25.4 mm. Source: I. Suzuki. 1989. Corrosion Resistant Coatings Technology, New York: Marcel Dekker.

a

Seashore

Coast

Inland shore of lake or marsh

Inland

Location

Average Corrosion Losses of Sacrificial Metal Coatings for 10 Years

TABLE 7.9

0.19

0.10

0.08

0.08

0.07

0.06

0.06

Root

Aluminum

0.07

0.04

0.04

0.03

0.03

0.02

0.02

Wall

Coatings 439


440


Aluminum and 55% Al–Zn alloy provide galvanic protection for the steel substrate. In rural and industrial atmospheres, an aluminum coating does not act as a sacrificial anode. However, in a chloride atmosphere such as a marine area, it does act as a sacrificial anode. The choice of what sacrificial metal coating to use will be based on the environment that it will be exposed to and the service life required. The service life required will also determine the coating thickness to be applied that, in turn, will influence the coating process to be used. Sacrificial metal coatings have been used successfully for roofs, walls, ducts, shutters, doors, and window frames in the housing industry; and on structural materials such as transmission towers, structural members of a bridge, antennae, chimney structures, grand-stands, steel frames, high-strength steel bolts, guard rails, corrugated steel pipe, stadium seats, bridge I-beams, footway bridges, road bridges, and fencing. 7.4.1 Zinc Coatings Approximately half of the world’s production of zinc is used to protect steel from rust. Zinc coatings are probably the most important type of metallic coating for corrosion protection of steel. The reasons for the wide application are: 1. Prices are relatively low. 2. Because of large reserves, an ample supply of zinc is available. 3. There is great flexibility in application procedures resulting in many different qualities with well-controlled layer thicknesses. 4. Steel provides good cathodic protection. 5. Many special alloy systems have been developed with improved corrosion protection properties. The ability to select a particular alloy or to specify a particular thickness of coating depends on the type of coating process used. Zinc coatings can be applied in many ways. The six most commonly used procedures follow. 7.4.1.1 Hot Dipping This is a process where cleaned steel is immersed in molten zinc or zinc alloy, and a reaction takes place to form a metallurgically bonded coating. The coating is integral with the steel because the formation process produces zinc–iron alloy layers overcoated with zinc. Continuity and uniformity is good since any discontinuities are readily visible as “black spots.” Coating thicknesses can be varied from approximately 50–125 mm on tube and products. Thicker coatings up to 250 mm can be obtained by grit-blasting before galvanizing. Sheet and wire normally receive thicknesses of 10–30 mm.


Coatings

441

Conventional coatings that are applied to finished articles are not formable. The alloy layer is abrasion resistant but brittle on bending. Special coatings with little or no alloy layer are readily formed (e.g., on sheet) and resistance welded. A chromate conversion coating over the zinc coating prevents wet storage stain, whereas, phosphate conversion coatings provide a good base (on a new sheet) for paints. Weathered coatings are often painted after 10–30 years for longer service. Hot-dip galvanizing is the most important zinc coating process. All mild steels and cast iron can be coated by this process. The thickness and structure of the coating will depend on the alloying elements. Approximately half of the steel that is coated is in the form of sheet, approximately one quarter is fabricated work, and the remainder is tube or wire. Metallurgically, the processes used for tubes and fabricated work is similar, whereas, the process used for sheet has small additions to the zinc that reduces the quantity of iron–zinc alloy in the coating which provides flexibility. 7.4.1.2 Zinc Electroplating This process is sometimes mistakenly referred to as electrogalvanizing. In this process, zinc salt solutions are used in the electrolytic deposition of a layer of zinc on a cleaned steel surface. This process provides good adhesion, comparable with other electroplated coatings. The coating is uniform within the limitations of “throwing power” of the bath. Pores are not a problem as exposed steel is protected by the adjacent zinc. Coating thickness can be varied at will but is usually 2.5–15 mm. Thicker layers are possible but are not generally economical. Electroplated steel has excellent formability and can be spot welded. Small components are usually finished before being plated. Chromate conversion coatings are used to prevent wet storage stain, whereas, phosphate conversion coatings are used as a base for paint. The process is normally used for simple, fairly small components. It is suitable for barrel plating or for continuous sheet and wire. No heating is used in this process except for hydrogen embrittlement relief on high strength steels. Electroplated zinc is very ductile, and consequently, this process is widely used for the continuous plating of strip and wire where severe deformation may be required. The coating on steel from this process gives a bright and smooth finish. It is used for decorative effect to protect delicate objects where rough or uneven finishes cannot be tolerated (e.g., instrument parts). It is also used for articles that cannot withstand the pretreatment or temperatures required in other coating processes. It was previously mentioned that the term electrogalvanizing is sometimes used to describe this process. This is misleading since the chief characteristic


442


of galvanizing is the formation of a metallurgical bond at the zinc–iron interface. This does not occur in electroplating. 7.4.1.3 Mechanical Coating This process involves the agitating of suitably prepared parts to be coated with a mixture of nonmetallic impactors (e.g., glass beads), zinc powder, a chemical promoter, and water. All types of steel can be coated. However, this process is less suitable for parts heavier than 1/2 lb (250 g) because the tumbling process reduces coating thickness at the edges. The adhesion is good compared with electroplated coatings. Thickness can be varied as desired from 5 mm to more than 70 mm. However, the coating is not alloyed with the steel nor does it have the hard, abrasion resistance iron–zinc alloy layers of galvanized or sherardized coatings. Conversion coatings can be applied. 7.4.1.4 Sherardizing The articles to be coated are tumbled in a barrel containing zinc dust at a temperature just below the melting point of zinc, usually around 7168F/ 3808C. In the case of spring steels, the temperature used is somewhat lower. By means of a diffusion process, the zinc bonds to the steel forming a hard, even coating of zinc–iron compounds. The coating is dull gray in color and can readily be painted if necessary. The finish is continuous and very uniform, even on threaded and irregular parts. This is a very useful finish for nuts and bolts that, with proper allowance for thickness of coats, can be sherardized after manufacture and used without retapping the threads. The thickness of coating can be controlled. Usually, a thickness of 30 mm is used for outdoor applications while 15 mm is used indoors. 7.4.1.5 Thermally Sprayed Coatings In the process, droplets of semimolten zinc are sprayed from a special gun that is fed with either wire or powder onto a grit-blasted surface. The seimmolten droplets coalesce with some zinc oxide present at each interface between droplets. Electrical continuity is maintained both throughout the coating and with the iron substrate so that full cathodic protection can be obtained since the zinc oxide forms only a small percentage of the coating. The sprayed coating contains voids (typically 10–20% by volume) between coalesced particles. These voids have little effect on the corrosion protection because they soon fill up with zinc corrosion products and are thereafter impermeable. However, the use of a sealer to fill the voids improves appearance in service and adds to life expectancy, but more importantly, it provides a better surface for subsequent application of paints. There are no size or shape limitations regarding the use of this process.


Coatings

443

7.4.1.6 Zinc Dust Painting Zinc dust paints may be used alone for protection or as a primer followed by conventional top coats. More details will be found in Chapter 8. 7.4.1.7 Corrosion of Zinc Coatings In general, zinc coatings corrode in a similar manner as solid zinc. However, there are some differences. For example, the iron–zinc alloy present in most galvanized coatings has a higher corrosion resistance than solid zinc in neutral and acid solutions. At points where the zinc coating is defective, the bare steel is cathodically protected under most conditions. The corrosion of zinc coatings in air is an approximate straight line relationship between weight loss and time. Because the protective film on zinc increases with time in rural and marine atmospheres of some types, under these conditions, the life of the zinc may increase more than in proportion to thickness. However, this does not always happen. Zinc coatings are primarily used to protect ferrous parts against atmospheric corrosion. These coatings have good resistance to abrasion by solid pollutants in the atmosphere. General points to consider are: 1. Corrosion increases with time of wetness. 2. The corrosion rate increases with an increase in the amount of sulfur compounds in the atmosphere. Chlorides and nitrogen oxides usually have a lesser effect but are often very significant in combination with sulfates. Zinc coatings resist atmospheric corrosion by forming protective films consisting of basic salts, notably carbonate. The most widely accepted formula is 3Zn(OH)2$2ZnCO3. Environmental conditions that prevent the formation of such films, or conditions that lead to the formation of soluble films, may cause rapid attack on the zinc. The duration and frequency of moisture contact is one such factor. Another factor is the rate of drying because a thin film of moisture with high oxygen concentration promotes reaction. For normal exposure conditions, the films dry quite rapidly. It is only in sheltered areas that drying times are slow so that the attack on zinc is accelerated significantly. The effect of atmospheric humidity on the corrosion of a zinc coating is related to the conditions that may cause condensation of moisture on the metal surface and to the frequency and duration of the moisture contact. If the air temperature drops below the dew point, moisture will be deposited. The thickness of the piece, its surface roughness, and its cleanliness also influence the amount of dew deposited. Lowering the temperature of a metal surface below the air temperature in a humid atmosphere will cause moisture to condense on the metal. If the water evaporates quickly, corrosion is usually not severe, and a protective film is formed on the surface. If water from rain or snow remains in contact with zinc when access to air is


444


restricted and the humidity is high, the resulting corrosion can appear to be severe (wet-storage stain known as “white rust”) because the formation of a protective basic zinc carbonate is prevented. In areas having atmospheric pollutants, particularly sulfur oxides and other acid forming pollutants, time of wetness becomes of secondary importance. These pollutants can also make rain more acid. However, in less corrosive areas, time of wetness assumes a greater proportional significance. In the atmospheric corrosion of zinc, the most important atmospheric contaminent to be considered is sulfur dioxide. At relative humidities of about 70% or above, it usually controls the corrosion rate. Sulfur oxides and other corrosive species react with the zinc coating in two ways: dry deposition and wet deposition. Sulfur dioxide can deposit on a dry surface of galvanized steel panels until a monolayer of SO2 is formed. In either case, the sulfur dioxide that deposits on the surface of the zinc forms a sulfurous or other strong acid that reacts with the film of zinc oxide, hydroxide, or basic carbonate to form zinc sulfate. The conversion of sulfur dioxide to sulfur-based acids may be catalyzed by nitrogen compounds in the air (NOx compounds). This factor may affect corrosion rates in practice. The acids partially destroy the film of corrosion products that will then reform from the underlying metal, thereby, causing continuous corrosion by an amount equivalent to the film dissolved, hence the amount of SO2 absorbed. Chloride compounds have less effect than sulfur compounds in determining the corrosion rate of zinc. Chloride is most harmful when combined with acidity because of sulfur gases. This is prevalent on the coast in highly industrial areas. Atmospheric chlorides will lead to the corrosion of zinc, but to a lesser degree than the corrosion of steel, except in brackish water and flowing seawater. Any salt deposit should be removed by washing. The salt content of the atmosphere will usually decrease rapidly inland farther away from the coast. Corrosion also decreases with distance from the coast, but the change is more gradual and erratic because chloride is not the primary pollutant affecting zinc corrosion. Chloride is most harmful when combined with acidity resulting from sulfur gases. Other pollutants also have an effect on the corrosion of galvanized surfaces. Deposits of soot or dust can be detrimental because they have the potential to increase the risk of condensation onto the surface and hold more water in position. This is prevalent on upward-facing surfaces. Soot (carbon) absorbs large quantities of sulfur that are released by rainwater. In rural areas, overmanuring of agricultural land tends to increase the ammonia content of the air. The presence of normal atmospheric quantities of ammonia does not accelerate zinc corrosion, and petrochemical plants where ammonium salts are present show no accelerated attack on galvanized steel. However, ammonia will react with atmospheric sulfur oxides, producing ammonium sulfate that accelerates paint film corrosion as well as zinc corrosion. When ammonium reacts with NOK x compounds in


Coatings

445

the atmosphere, ammonium nitrite and nitrate are produced. Both compounds increase the rate of zinc corrosion, but less than SO2 or SO3. Because of the Mears effect (wire corrodes faster per unit of area than more massive materials) galvanized wire corrodes some 10–80% faster than galvanized sheet. However, the life of rope made from galvanized steel wires is greater than the life of the individual wire. This is explained by the fact that the parts of the wire that lie on the outside are corroded more rapidly and when the zinc film is penetrated in those regions, the uncorroded zinc inside the rope provides cathodic protection for the outer regions. Table 7.10 lists the compatibility of zinc coatings with various corrodents. TABLE 7.10 Compatibility of Galvanized Steel with Selected Corrodents Acetic Acid Acetone Acetonitrile Acrylonitrile Acrylic latex Aluminum chloride, 26% Aluminum hydroxide Aluminum nitrate Ammonia, dry vapor Ammonium acetate solution Ammonium bisulfate Ammonium bromide Ammonium carbonate Ammonium chloride, 10% Ammonium dichloride Ammonium hydroxide Vapor Reagent Ammonium molybdate Ammonium nitrate Argon Barium hydroxide Barium nitrate solution Barium sulfate solution Beeswax Borax Bromine, moist 2-Butanol Butyl acetate Butyl chloride Butyl ether Butylphenol Cadmium chloride solution Cadmium nitrate solution Cadmium sulfate solution Calcium hydroxide Sat. solution 20% Solution Calcium sulfate, sat. solution

U G G G U U U U U U U U U U U U U G U G S S U S U G G G G G U U U U S U

(continued)


446

Corrosion of Linings and Coatings TABLE 7.10 Continued Cellosolve acetate Chloric acid, 20% Chlorine, dry Chlorine water Chromium chloride Chromium sulfate solution Copper chloride solution Decyl acrylate Diamylamine Dibutylamine Dibutyl cellosolve Dibutyl phthalate Dichloroethyl ether Diethylene glycol Dipropylene glycol Ethanol Ethyl acetate Ethyl acrylate Ethyl amine, 69% N-Ethyl butylamine 2-Ethyl butyric acid Ethyl ether Ethyl hexanol Fluorine, dry, pure Formaldehyde Fruit juices Hexanol Hexylamine Hexylene glycol Hydrochloric acid Hydrogen peroxide Iodine, gas Isohexanol Isooctanol Isopropyl ether Lead sulfate Lead sulfite Magnesium carbonate Magnesium chloride, 42.5% Magnesium fluoride Magnesium hydroxide, sat. Magnesium sulfate 2% Solution 10% Solution Methyl amyl alcohol Methyl ethyl ketone Methyl propyl ketone Methyl isobutyl ketone Nickel ammonium sulfate Nickel chloride Nickel sulfate Nitric acid Nitrogen, dry, pure Nonylphenol Oxygen Dry, pure Moist

G U G U U U U G G G G G G G G G G G G G G G G G G S G G G U S U G G G U S S U G S S U G G G G U U S U G G G U

(continued)


Coatings

447 TABLE 7.10

Continued

Paraldehyde Perchloric acid solution Permanganate solution Peroxide Pure, dry Moist Phosphoric acid, 0.3–3% Polyvinyl acetate latex Potassium carbonate 10% Solution 50% Solution Potassium chloride solution Potassium bichromate 14.7% 20% Potassium disulfate Potassium fluoride, 5–20% Potassium hydroxide Potassium nitrate 5–10% Solution Potassium peroxide Potassium persulfate, 10% Propyl acetate Propylene glycol Propionaldehyde Propionic acid Silver bromide Silver chloride Pure, dry Moist, wet Silver nitrate solution Sodium acetate Sodium aluminum sulfate Sodium bicarbonate solution Sodium bisulfate Sodium carbonate solution Sodium chloride solution Sodium hydroxide solution Sodium nitrate solution Sodium sulfate solution Sodium sulfide Sodium sulfite Styrene, monomeric Styrene oxide Tetraethylene glycol 1,1,2 Trichloroethane 1,2,3 Trichloropropane Vinyl acetate Vinyl ethyl ether Vinyl butyl ether Water Potable, hard

G S S S U G U U U U G S S G U S U U G G G U U S U U S U U U U U U U U U U G G G G G G G G G

G, suitable application; S, borderline application; U, not suitable.


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7.5 Zinc–5% Aluminum Hot-Dip Coatings This zinc alloy coating is known as Galfan. Galfan coatings have a corrosion resistance up to three times that of galvanized steel. The main difference between these two coatings lies in the degree of cathodic protection they afford. This increase in corrosion protection is evident in both a relatively mild urban industrial atmosphere as can be seen in Table 7.11. The latter is particularly significant, because, unlike galvanizing, the corrosion rate appears to be slowing after about four years, and conventional galvanized steel would show rust in Five years. See Figure 7.16. The slower rate of corrosion also means that the zinc–5% aluminum coatings provide full cathodic protection to cut edges over a longer period. Refer to Table 7.12. Because Galfan can be formed with much smaller cracks than can be obtained in conventional galvanized coatings, it provides excellent protection at panel bulges. This reduced cracking means that less zinc is exposed to the environment that increases the relative performance factor compared with galvanized steel.

7.6 Zinc–55% Aluminum Hot-Dip Coatings These coatings are known as Galvalume and consist of zinc–55% aluminum– 1.5% silicon. This alloy is sold under such tradenames as Zaluite, Aluzene, Alugalva, Algafort, Aluzink, and Zincalume. Galvalume exhibits superior corrosion resistance over galvanized coatings in rural, industrial, marine, and severe marine environments. However, this alloy has limited cathodic protection and less resistance to some alkaline conditions and is subject to weathering discoloration and wet storage staining. The latter two disadvantages can be overcome by chromate passivation that also improves its atmospheric corrosion resistance.

TABLE 7.11 Five-Year Outdoor Exposure Results of Galfan Coating Thickness Loss (mm) Atmosphere Industrial Severe marine Marine Rural

Galvanized

Galfan

Ratio of Improvement

15.0 O20.0 12.5 10.5

5.2 9.5 7.5 3.0

2.9 O2.1 1.7 3.5

Source: From F.C. Porter. 1994. Corrosion Resistance of Zinc and Zinc Alloys, New York: Marcel Dekker.


Coatings

449 20 o = Galvanized x = Galfan

1-side thickness loss (μm)

15

10

5

0

12

24

36

48

60

72

84

96

Exposure time (months) FIGURE 7.16 Seven year exposure of Galfan and galvanized steel in a severe marine atmosphere.

Initially, a relatively high corrosion loss is observed for Galvalume sheet as the zinc-rich portion of the coating corrodes and provides sacrificial protection at cut edges. This takes place in all environments, whereas, aluminum provides adequate galvanic protection only in marine chloride

TABLE 7.12 Comparison of Cathodic Protection for Galfan and Galvanized Coatings Amount (mm) of Bare Edges Exposed after 3 Years (Coating Recession from Edge) Environment

Galvanized

Galfan

Severe marine Marine Industrial Rural

1.6 0.5 0.5 0.1

0.1 0.06 0.05 0

Source: From F.C. Porter. 1994. Corrosion Resistance of Zinc and Zinc Alloys, New York: Marcel Dekker.


450


15

Galvanized

Corrosion loss, micrometers


environments. After approximately three years, the corrosion-time curves take on a more gradual slope reflecting a change from active, zinclike behavior to passive, aluminumlike behavior as the interdentric regions fill with corrosion products. It has been predicted that Galvalume sheets should outlast galvanized sheets of equivalent thickness by at least two to four times over a wide range of environments. Figures comparing the corrosion performance of galvanized sheet and Galvalume sheet are shown in Figure 7.17. Galvalume sheets provide excellent cut-edge protection in very aggressive conditions where the surface does not remain too passive. However, it does not offer as good a protection on the thicker sheets in mild rural conditions

10

5

0

Galvalume

0

2

15

10 Galvalume 5

0

4 6 8 10 12 14 16 Exposure time, years

Galvanized

0

4 6 8 10 12 14 16 Exposure time, years

Severe marine atmosphere

Marine atmosphere


2

Galvanized

15

10

5

Galvalume 0

0

2

4 6 8 10 12 14 16 Exposure time, years Industrial atmosphere

FIGURE 7.17 Thirteen year exposure of Galvalume in marine and industrial atmospheres.


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451

where zinc–5% aluminum coatings provide good general corrosion resistance, and when sheared edges are exposed or localized damage to the coating occurs during fabrication or service, the galvanic protection is retained for a longer period.

7.7 Zinc–15% Aluminum Thermal Spray Zinc–15% aluminum coatings are available as thermally sprayed coatings. These coatings have a two-phase structure consisting of a zinc-rich and an aluminum-rich phase. The oxidation products formed are encapsulated in the porous layer formed by the latter and do not build up a continuous surface layer as with pure zinc coatings. As a result, no thickness or weight loss is observed even after several years of exposure in atmospheric field testing. It is normally recommended that thermally sprayed coatings be sealed to avoid initial rust stains, to improve appearance, and to facilitate maintenance painting. Sealing is designed to fill pores and give only a thin overall coating, too thin to be directly measurable. Epoxy or acrylic system resin, having a low viscosity, is used as a sealer.

7.8 Zinc–Iron Alloy Coatings As compared with pure zinc, the zinc–iron alloy coatings provide increased corrosion resistance in acid atmospheres, but slightly reduced corrosion resistance in alkaline atmospheres. Electroplated zinc–iron alloy layers containing more than 20% iron provide a corrosion resistance 30% higher than zinc in industrial atmospheres. In other atmospheres, the zinc–iron galvanized coatings provide as good a coating as coatings with an outer zinc layer. Sherardized coatings are superior to electroplated coatings and equal to galvanized coatings of the same thickness. However, the structure of the alloy layer, and its composition, affects the corrosion resistance. If the zinc layer of a galvanized coating has weathered, or the zinc–iron alloy layer forms the top layer after galvanizing, brown areas may form. Brown staining can occur on sherardized or hot dip galvanized coatings in atmospheric corrosion through the oxidation of iron from the zinc–iron alloy layers or from the substrate. Such staining is usually a dull brown rather than the bright red–brown of uncontrolled rust. Usually, there is a substantial intact galvanized layer underneath, leaving the life of the coating unchanged. Unless the aesthetic appearance is undesirable, no action need be taken.


452


7.9 Aluminum Coatings Aluminum coatings protect steel substrates by means of cathodic control, with an original barrier action of an air formed film which is chemically inert, and the rapid formation of oxide film by a self-healing ability. Aluminum coatings are excellent in general corrosion resistance. However, they do not act as a sacrificial anode in rural and industrial atmospheres but do in a chloride area such as a marine environment. In a nonchloride environment, the formation of red rust occurs at sheared edges and in other defects of an aluminum coating layer. However, the growth of red rust is slow. Aluminum coatings, sealed with organic or composite layers, such as etch primer, zinc chromate, etc., will provide long service in seawater environments. Recommended coating thickness plus sealing for the splash zone and submerged zone is 150 mm.

7.10 Cadmium Coatings Cadmium coatings are produced almost exclusively by electrodeposition. A cadmium coating on steel does not provide as much cathodic protection to the steel as does a zinc coating because the potential between cadmium and iron is not as great as between zinc and iron. Therefore, it becomes important to minimize defects in the cadmium coating. Unlike zinc, a cadmium coating will retain a bright metallic appearance. It is more resistant to attack by salt spray and atmospheric condensate than zinc. In aqueous solutions, cadmium will resist attack by strong alkalies, but will be corroded by dilute acids and aqueous ammonia. Cadmium coatings should not be allowed to come into contact with food products because cadmium salts are toxic. This coating is commonly used on nuts and bolts, but because of its toxicity, usage is declining.

7.11 Manganese Coatings Manganese is very active, having an electrode potential more negative than zinc (Mn: K1.5 m, Zn K1.03 V, SCE). In a natural atmosphere, a dense corrosion layer builds on the surface of manganese during a very short period. However, defects in the coating accelerate the anodic dissolution of manganese, thereby, shortening the life of the coating. Therefore, manganese is combined with zinc to form a duplex Mn/Zn alloy coating. The types of corrosion products found on these coatings were shown in Table 7.7. The compound g-Mn2O3 is effective for the formation of a barrier. The more g-Mn2O3 in the corrosion products, the denser the layer on a Mn/Zn coating.


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453

Manganese is so negative in electrochemical potential, and active, that its alloy and duplex coatings provide galvanic protection. Mn/Zn alloy coating exhibits high corrosion resistance, and the corrosion potential of manganese is more negative than that of zinc; therefore, this alloy coating provides cathodic protection for a steel substrate. The structure of Mn/Zn alloy coating is composed of the single phase of 3 in the manganese content range !20%, and 3 and g phases in the range above 20%. As the manganese content in the deposit is increased, the percentage of g-Mn phase is increased.

7.12 Conversion Coatings The term conversion coating is used to describe coatings where the substrate metal provides ions that become part of the protective coating. The coating layers are composed of inorganic compounds that are chemically inert. These inert compounds on the surface reduce both anodic and cathodic areas and delay the transit of reactive species to the base metal. This results in increases in the slopes of anodic and cathodic polarization curves, thereby, decreasing the rate of corrosion of the substrate. Conversion layers are used for various reasons: 1. To improve the adherence of the organic layers 2. To obtain electrically insulating barrier layers 3. To provide a uniform grease-free surface 4. To provide active corrosion inhibition by reducing the rate of the oxygen reduction reaction or by passivating the metallic substrate Conversion coatings belonging in this group are phosphate, chromate, oxide, and anodized coatings. These coatings are composed of corrosion products that have been artificially formed by chemical or electrochemical reactions in selected solutions. The corrosion products formed build a barrier protection for the substrate metal. This barrier reduces the active surface area on the base metal, thereby, delaying the transport of oxidizers and aggressive species. By doing so the coating inhibits the formation of corrosion cells. The degree of secondary barrier action depends on the compactness, continuity, and stability of the corrosion product layer. Each conversion coating protects the base metal against corrosion with two or three of the following protective abilities: 1. Secondary barrier action of corrosion products 2. Inhibiting action of soluble compounds contained in the corrosion products 3. Improvement in paint adhesion by the formation of a uniform corrosion product layer


454


7.12.1 Phosphate Coating When a metal surface is treated with a weak phosphoric acid solution of iron, zinc, or manganese phosphate, phosphate layers are formed. These phosphate coatings are applied to iron and steel, zinc, aluminum, and their alloys. Phosphate films are formed by the dissolution of base metal and the precipitation of phosphate films. The metal surface must be free of greases, oils, and other carbonaceous material before immersion in the phosphating solution or before spray application. Baths operating at 1208F/508C have pH values of approximately 2, whereas, those operating below 1208F/508C have pH values of approximately 3. The zinc phosphate coating is basically the result of a corrosion process. Reactions of iron and steel in a zinc phosphate solution are as follows: 1. The dissolution of base metal at the anodic sites: Fe C 2H3 PO4 / FeðH2 PO4 Þ2 C H2

(7.23)

Promotion by the activator: C 2Fe C 2H2 POK 4 C 2H C 3NO2 / 2FePO4 C 3H2 O C 3NO

4Fe C 3Zn

2C

C 6H2 POK 4 C 6NO2 / 4FePO4

(7.24)

C Zn3 ðPO4 Þ2

C 6H2 O C 6NO

(7.25)

2. Precipitation of phosphate films at the cathodic sites: 2ZnðH2 PO4 Þ2 C FeðH2 PO4 Þ2 C 4H2 O / Zn2 FeðPO4 Þ2 $4H2 O C4H3 PO4 |fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}

(7.26)

Phosphophyllite

3ZnðH2 PO4 Þ2 C 4H2 O/ Zn3 ðPO4 Þ2 $4H2 O C4H3 PO4 |fflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflffl}

(7.27)

Hopeite

With these reactions, the phosphate film consists of phosphophyllite and hopeite. Phosphate solubilities are lowest in the pH range of 6–8. They are stable in neutral environments and are nonelectric conductive compounds. Phosphate film deposits on cathodic areas and anodic sites remain in the form of pinholes. Consequently, the continuity of phosphate films is not as good as those of anodic oxide and chromate films. Since the barrier action of a conversion film is dependent on its solubility and continuity, it is evident that the phosphate films provide only limited protection. However, they do provide an excellent base for paint, plastic, and rubber coatings.


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455

The chemical effects of phosphating on the surface is to convert the surface to a nonalkaline condition, protecting the surface from reactions with oils in paint and to protect against the spread of corrosion from defects. Alkaline residues on the surface of the base metal lead to underfilm corrosion. Phosphating increases the uniformity in the surface texture and surface area that improves paint adhesion, that in turn, increases the service life of a paint film. 7.12.2 Chromate Coating Chromate conversion coatings are formed on aluminum and its alloys— magnesium, zinc, and cadmium. These coatings provide good corrosion protection and improve the adhesion of organic layers. A chromate coating is composed of a continuous layer consisting of insoluble trivalent chromium compounds and soluble hexavalent chromium compounds. The coating structure provides a secondary barrier, inhibiting action, and also good adhesion for lacquer films. Chromate coatings provide their corrosion resistance based on the following three properties: 1. Cr(III) oxide, that is formed by the reduction of Cr(IV) oxide, has poor solubility in aqueous media and, thereby, provides a barrier layer. 2. Cr(VI) will be included in the conversion coating and will be reduced to Cr(III) to passivate the surface when it is damaged, preventing hydrogen gas from developing. 3. The rate of cathodic oxygen reactions is strongly reduced. Most chromate conversion coatings are amorphous gel-like precipitates, so they are excellent in continuity. The service life is dependent on thickness, characteristics of the base metal, coating conditions—particularly dry heat— and the environmental conditions that the chromated products are used under. When a chromated product is exposed to the atmosphere, hexavalent chromium slowly leaches from the film, with the result that the surface appearance changes from irridescent yellow to either a green color or to clear. The structure of the film consists of more of the insoluble trivalent chromium compounds. Passivation is provided for any damaged areas by the leached hexavalent chromium. The longer the time of wetness, the shorter the service life of the coating because chromate coatings absorb moisture, and moisture results in the leaching of hexavalent chromium. The leaching behavior of a chromate film is also affected by its aging process, drying process, and long-term storage. Aging of a chromate coating reduces its protective ability.


456


Chrome baths always contain a source of hexavalent chromium ion (e.g., chromate, dichromate. or chromic acid) and an acid to produce a low pH that usually is in the range of 0–3. A source of fluoride ions is also usually present. These fluoride ions will attack the original (natural) aluminum oxide film, exposing the base metal substrate to the bath solution. Fluoride also prevents the aluminum ions (that are released by the dissolution of the oxide layer) from precipitating by forming complex ions. The fluoride concentration is critical. If the concentration is too low, a conversion layer will not form because of the failure of the fluoride to attack the natural oxide layer, whereas, too high a concentration results in poor adherence of the coating because of reaction of the fluoride with the aluminum metal substrate. During the reaction, hexavalent chromium is partially reduced to trivalent chromium, forming a complex mixture consisting largely of hydrated hydroxides of both chromium and aluminum: 6HC C H2 Cr2 O7 C 6eK/ 2CrðOHÞ3 C H2 O

(7.28)

There are two types of processes that can produce conversion coatings: chromic acid processes and chromic acid–phosphoric acid processes. In the formation of the chromic acid-based conversion coating, the following overall equation governs: 6H2 Cr2 O7 C 3OHF C 12Al C 18HNO3 / 3Cr2 O3 C Al2 O3 C 10AlF3 C 6CrðNO3 Þ3 C 30H2 O

(7.29)

The oxide Cr2O3 is better described as an amorphous chromium hydroxide, Cr(OH)3. The conversion coating is yellow to brown in color. In the chromic acid–phosphoric acid process the following reaction governs: 2H2 Cr2 O7 C 10H3 PO4 C 12HF C 4Al/ CrPO4 C 4AlF C 3CrðH2 PO4 Þ3 C 14H2 O This conversion coating is greenish in color and primarily consists of hydrated chromium phosphate with hydrated chromium oxide concentrated toward the metal. The barrier action of a chromate coating increases with its thickness. Chromate conversion coatings can be used as a base for paint or alone for corrosion protection. Previously, it was described how the leached hexavalent chromium acts as an anodic inhibitor, by forming passive films over defects in the coating. Since the films formed on aluminum by the chromic acid–phosphoric acid process contain no hexavalent chromium, they do not provide self-healing from defects.


Coatings

457

The service life of a chromate coating depends on the coating thickness. Chromate coatings absorb moisture, and moisture results in the leaching of hexavalent chromium. Therefore, the longer the time of wetness, the shorter the life of the coating. However, as long as the leaching of the hexavalent chromium continues, the base metal is protected. Environmental conditions, particularly time of wetness and temperature, determine the leaching rate. In natural environments, the leaching rate is commonly low. Pollutants in the atmosphere, particularly chloride ions, also increase the rate of deterioration of the film. Chromate conversion coatings provide good corrosion resistance in a mild atmosphere, such as indoor atmospheres, and surface appearance. They also provide a good base for organic films. Chromate conversion coatings are usually applied to zinc and its alloy coated sheets, to protect against staining during storage, and to products of zinc-die castings, aluminum and its alloys, and magnesium and its alloys. 7.12.3 Oxide Coatings Iron or steel articles to be coated are heated in a closed retort to a temperature of 16008F/8718C; afterwards, superheated steam is admitted. This results in the formation of red oxide (Fe2O3) and magnetic oxide (Fe3O4). Carbon monoxide is then admitted to the retort, reducing the red oxide to magnetic oxide that is resistant to corrosion. Each operation takes approximately 20 min. Iron and steel may also be oxide coated by electrolytic means. The article to be coated is made the anode in an alkaline solution (anodic oxidation). These coatings are primarily for appearance such as for cast iron stove parts. 7.12.4 Anodized Coatings The electrochemical treatment of a metal serving as an anode in an electrolyte is known as anodizing. Since aluminum’s electrode potential is negative and its oxide film is stable in natural environments, surface treatments have been developed for the purpose of producing more stable oxide films. The anodic films formed can be either porous or nonporous depending upon which electrolyte is used. Porous films result when electrolytes such as sulfuric acid, oxalic acid, chromic acid, and phosphoric acid are used. These films have the advantage of being able to be dyed. Sulfuric acid is the most widely used electrolyte. A large range of operating conditions can be utilized to produce a coating to meet specific requirements. Hard protective coatings are formed that serve as a good base for dyeing. In order to obtain the maximum corrosion resistance, the porous coating must be sealed after dyeing. The anodic coating formed, using sulfuric acid as the electrolyte, is clear and transparent on pure


458


aluminum. Aluminum alloys containing silicon or manganese and the heterogeneous aluminum–magnesium alloy yield coatings that range from gray to brown and may be patchy in some cases. The adsorptive power of these coatings make them excellent bases for dyes, especially if they are sealed in nickel or cobalt acetate solution. It is not recommended to use sulfuric acid as the electrolyte for anodizing work containing joints that can retain the sulfuric acid after removal from the bath. The retained electrolyte will provide sites for corrosion. When chromic acid is used as the electrolyte, the coatings produced are generally opaque, gray, and irridescent, with the quality being dependent on the concentration and purity of the electrolyte. These are unattractive as compared to those formed using sulfuric acid as the electrolyte. When 0.03% sulfate is added to the electrolyte, colorless and transparent coatings are formed. These coatings are generally thin, of low porosity, and difficult to dye. Black coatings can be obtained in concentrated solutions at elevated temperatures. Attractive opaque surfaces can be obtained by adding titanium, zirconium, and thallium compounds to the electrolyte. The chromic acid anodizing process is the only one that can be used on structures containing blind holes, crevices, or difficult to rinse areas. Chromic acid anodizing generally increases fatigue strength, whereas, sulfuric acid anodizing may produce decreases in fatigue strength. Boric acid electrolytes produce a film that is irridescent and oxides in the ˚ . The coating is essentially nonporous. range of 2500–7500 A Oxalic and other organic acids are electrolytes used to produce both protective and decorative films. Unsealed coatings are generally yellow in color. These films are harder and more abrasion resistant than the conventional sulfuric acid films. However, the specially hard coatings produced under special conditions in sulfuric acid electrolytes are superior. The anodized coating consists of two major components: the nonporous barrier layer adjoining the metal and a porous layer extending from the barrier layer to the outer portion of the film. Sulfuric, chromic, and oxalic acid electrolytes form both barrier and porous layers, whereas, boric acid electrolytes produce only barrier films. Anodizing of aluminum provides long-term corrosion resistance and decorative appearance. Corrosion of the anodized film is induced by SOx gas and depositions of grime, sulfates, and chlorides. These depositions promote corrosion because they tend to absorb aggressive gases and moisture, thereby, increasing the time of wetness and decreasing the pH of the electrolyte at the interface between the depositions and the surface. Although rain increases the time of wetness, it has the effect of cleaning the surface rather than making the surface corrosive. Some of the depositions are removed by the rain. Cleaning with water is one method that helps to protect the anodized aluminum from corrosion. In marine atmospheres, the depositions can be removed with water because the depositions are primarily soluble chlorides. However, in industrial atmospheres, detergents are needed because the deposits are greasy.


Coatings

459

SOx gas is the most aggressive pollutant for anodic films. The corrosive effect is dependent on the concentration, with the corrosion area increasing linearly with concentration.

7.13 Organic Coatings Organic coatings are widely used to protect metal surfaces from corrosion. The effectiveness of such coatings is dependent not only on the properties of the coatings, that are related to the polymeric network and possible flaws in this network, but also on the character of the metal substrate, the surface pretreatment, and the application procedures. Therefore, when considering the application of a coating, it is necessary to take into account the properties of the entire system. There are three broad classes of polymeric coatings: lacquers, varnishes, and paints. Varnishes are materials that are solutions of either a resin alone in a solvent (spirit varnishes) or an oil and resin together in a solvent (oleoresinous varnishes). A lacquer is generally considered to be a material whose basic film former is nitrocellulose, cellulose acetate–butyrate, ethyl cellulose, acrylic resin, or another resin that dries by solvent evaporation. The term paint is applied to more complex formulations of a liquid mixture that dries or hardens to form a protective coating. Organic coatings provide protection either by the formation of a barrier action from the layer or from active corrosion inhibition provided by pigments in the coating. In actual practice, the barrier properties are limited because all organic coatings are permeable to water and oxygen to some extent. The average transmission rate of water through a coating is about 10–100 times larger than the water consumption rate of a freely flowing surface, and in normal outdoor conditions, an organic coating is saturated with water at least half of its service life. For the remainder of the time, it contains a quantity of water comparable in its behavior to an atmosphere of high humidity. Table 7.13 shows the diffusion data for water through organic films. It has also been determined that, in most cases, the diffusion of oxygen through the coating is large enough to allow unlimited corrosion. Taking these factors into account indicates that the physical barrier properties alone do not account for the protective action of coatings. Table 7.14 shows the flux of oxygen through representative free films of paint 100 mm thick. Additional protection may be supplied by resistance inhibition that is also a part of the barrier mechanism. Retardation of the corrosion action is accomplished by inhibiting the charge transport between cathodic and anodic sites. The reaction rate may be reduced by an increase in the electrical resistance and/or the ionic resistance in the corrosion cycle. Applying an organic coating on a metal surface increases the ionic resistance.


460


TABLE 7.13 Diffusion Data for Water through Organic Films Polymer Epoxy Phenolic Polyethylene (low density) Polymethyl methacrylate Polyisobutylene Polystyrene Polyvinyl acetate Polyvinyl chloride Vinylidene chloride/ acrylonitrile compolymer

Temperature 8C

p!109 (cm3 (STP)cm)

25 40 25 25 50 30 25 40 30 25

10–44 — 166 9 250 7–22 97 600 13 1.7

D!109 cm2/s 2–8 5 0.2–10 230 130 — — 150 16 0.32

Source: From H. Leidheiser Jr. 1987. Coatings, in Corrosion Mechanisms, F. Mansfield, Ed., New York: Marcel Dekker, pp. 165–209.

The electronic resistance may be increased by the formation of an oxide film on the metal. This is the case for aluminum substrates. Corrosion of a substrate beneath an organic coating is an electrochemical process that follows the same principles as corrosion of an uncoated substrate. It differs from crevice corrosion because the reactants often reach the substrate through a solid. In addition, during the early stages of corrosion, small volumes of liquid are present, resulting in extreme values of pH and ion concentrations. The total corrosion process takes place as follows: 1. Migration through the coating of water, oxygen, and ions

TABLE 7.14 Flux of Oxygen through Representative Free Films of Paint, 100 mm Thick Paint Alkyd (15% PVC Fe2O3) Alkyd (35% PVC Fe2O3) Alkyl melamine Chlorinated rubber (35% PVC Fe2O3) Cellulose acetate Cellulose nitrate Epoxy melamine Epoxy coal-tar Epoxy polyamide (35% PVC Fe2O3) Vinyl chloride/vinyl acetate copolymer

J ( mg/cm2 day) 0.0069 0.0081 0.001 0.017 0.026 (95% RH) 0.115 (95% RH) 0.008 0.0041 0.0064 0.004 (95% RH)

Source: From H. Leidheiser Jr. 1987. Coatings, in Corrosion Mechanisms, F. Mansfield, Ed., New York: Marcel Dekker, pp. 165–209.


Coatings

461

2. Development of an aqueous phase at the coating/substrate interface 3. Activation of the substrate surface for the anodic and cathodic reactions 4. Deterioration of the coating/substrate interfacial bond 7.13.1 Composition of Organic Coatings The composition of a coating (paint) determines the degree of corrosion protection that will be supplied. A paint formulation is made up of four general classes of ingredients: vehicle (binder, resin component), pigment, filler, and additive. It is the combination of these ingredients that impart the protective properties to the coating. 7.13.1.1 Resin Component The resin component is also known as the vehicle or binder, but resin component is more descriptive. The resin is the film-forming ingredient of the paint. It forms the matrix of the coating, the continuous polymeric phase that all other components may be incorporated in. Its density and composition largely determine the permeability, corrosion resistance, and UV resistance of the coating. The most common resins used are vinyls, chlorinated rubber, acrylics, epoxies, urethanes, polyester, autooxidative cross-linking coatings, and water soluble resins. 7.13.1.1.1 Vinyl Resins Vinyl is the general term denoting any compound containing the vinyl linkage (–CHaCH 2) group. However, there are many compounds containing this linkage that are not considered as vinyl coatings such as styrene and propylene. Vinyl coatings are primarily considered to be copolymers of vinyl chloride and vinyl acetate having the chemical structure shown in Figure 7.18.

H

H

H

H

C

H

C

O

H C

C CL

H

C

C H

H

C

O

H

C

CH3

H

C CL O

O

H

C

CH3

FIGURE 7.18 Chemical structure of vinyl acetate and vinyl chloride copolymer.


462


A relatively large amount of solvent is required to dissolve a vinyl copolymer high in vinyl chloride content. Because of this, the volume of solids in the solution is relatively low. As a result, most vinyl coatings must be applied in thin (1–1.5 mil) coats. Consequently, a vinyl coating system might require five or more coats. The system is considered highly labor intensive, even though in the proper environment excellent protection is provided. A formulation has been developed that permits 2–2.5 mils to be applied per coat, but this advantage comes at the expense of reduced protection. The thixotropes, fillers, and additives used to permit the greater thicknesses are more susceptible to environmental and moisture penetration. 7.13.1.1.2 Chlorinated Rubber Chlorinated rubber resins include those resins produced by the chlorination of both natural and synthetic rubbers. Chlorine is added to unsaturated double bonds until the final product contains approximately 65% chlorine with the chemical structure shown in Figure 7.19. Since the final product is a hard, brittle material with poor adhesion and elasticity, a plasticizer must be added. The volume of solids of the coating is somewhat higher than that of a vinyl; therefore, a suitably protective chlorinated rubber system often consists of only three coats. 7.13.1.1.3 Acrylics The acrylics can be formulated as thermoplastic resins, thermosetting resins, and as a water-emulsion latex. The resins are formed from polymers of acrylate esters, primarily polymethyl methacrylate and polyethyl acrylate. Because the acrylate resins do not contain tertiary hydrogens attached directly to the polymer backbone chain, they are exceptionally stable to oxygen and UV light. The repeating units for the methacrylate and acrylate are as follows: CH2

CH3 CH2 C

C

C

O

C

CH OCH2

CH3

CH53

Polymethacrylate

Polyethyl acrylate

7.13.1.1.4 Epoxies Epoxy resins are not suitable for protective coatings because when pigmented and applied they dry to a hard, brittle film with very poor chemical resistance. When copolymerized with other resins, specifically with those of the amine or polyamide family, or with esterfied fatty acids, epoxy resins will form a durable protective coating.


CH3

FIGURE 7.19 Chemical structure of chlorinated rubber.

C

C

Cl

CH3 C Cl

Cl C H H H

Cl

C Cl

C Cl

C

CH3 C Cl

Cl

C

C Cl

C

Cl

H

H

H

H H

H

CH3 H

CH3

C Cl

C Cl

C Cl

C Cl

C Cl

C

Cl

C

CH3 C Cl

Cl

C

C Cl Cl C H

H

H

C

Cl

C

H

Cl C H

C Cl

H

Cl

C

H

Coatings 463


464


7.13.1.1.5 Urethanes Urethanes are reaction products of isocyanates with materials having hydroxyl groups and simply contain a substantial number of urethane groups (–N–C–O–) regardless of what the rest of the molecule may be. The hydroxyl containing side might consist of a variety of compounds including water (moisture cured urethanes), epoxies, polyesters, acrylics, and drying oils. Figure 7.20 shows several typical chemical structures. Epoxy and polyester polyols, though more expensive than the acrylic polyols, are more chemically and moisture resistant. However, the acrylic polyol, when suitably reacted to form a urethane coating, is satisfactory for weathering atmospheres. Coatings formulated with aliphatic isocyanates cost approximately twice as much as similar coatings formulated with epoxy and aromatic isocyanates. However, they have superior color and gloss retention and are resistant to deterioration by sunlight. Aliphatic urethanes will continue to maintain a glossy “wet” look years after application, whereas, other urethane coatings will chalk or yellow somewhat after exposure to the sun. 7.13.1.1.6 Polyesters In the coating industry, polyesters are characterized by resins based on components that introduce unsaturation (–CaC–) directly into the polymer backbone. Typical is the structure of an isophthalic polyester resin as shown in Figure 7.21. The most common polyester resins are polymerized products of maleic or isophthalic anhydride or their acids. In producing paint, the polyester resin is dissolved in styrene monomer, together with pigment and small amounts of a reaction inhibitor. A free radical initiator, commonly a peroxide, and additional styrene are packaged in another container. When applied, the containers are mixed; sometimes, because of the fast initiating

H O H R N C O +

R NH2

R N C N R

with an amine H O R N C O +

R N C R

H O

O

R N C N C R

with an amide

R H O H

R N C O + HOH

R NH2 + CO2 + R N C O

R N C N R

with moisture FIGURE 7.20 Typical structure of urethane coating.


Coatings

465

C

C

OH C C C C

H

C

C

O C O C

H H

H H

C

C

H H

C O C O C C C C C

H

H H

O C C OH

H H

H H n

n=3−6 FIGURE 7.21 Chemical structure of polyester coating.

reaction (short pot life), they are mixed in an externally mixing or dualheaded spray gun. After being mixed and applied, a relatively fast reaction takes place, resulting in cross-linking and polymerization of the monomeric styrene with the polyester resin. Another class of coatings, formulated in a similar manner, are the vinyl esters, The vinyl esters derive from a resin based on a reactive end vinyl group that can open and polymerize. The chemical structure is shown in Figure 7.22. 7.13.1.1.7 Autooxidative Cross-Linking Coatings Autooxidative cross-linking coatings rely on a drying oil with oxygen to introduce cross-linking within the resin and attainment of final film

H H C H

H

O

H OH

C C C O

C C O

H

H H

H OH H C

O

O

H

C C

C O C C C

H H

H

H C H H

n FIGURE 7.22 Chemical structure of vinyl acetate coating.


H H

466


properties. The final coating is formed as a result of the drying oil reacting with the resin that is combined with pigments and solvents. The paint is packaged in a single can that can be opened, mixed, and the paint applied. Since oxygen reacts with the coating, introducing additional cross-linking, final film properties can take weeks or even months to attain. Autooxidative cross-linking type paints include alkyds, epoxies, esters, oil-modified urethanes, and so on. These are commonly used, when properly formulated, to resist moisture and chemical fume environments. They can be applied over wood, metal, or masonry substrates. The advantage of these coatings is their ease of application, excellent adhesion, relatively good environmental resistance (in all but immersion and high chemical fume environment), and tolerance for poorer surface preparation. Their major disadvantage, compared with other synthetic resins, is their lessened moisture and chemical resistance. 7.13.1.1.8 Water Soluble Resins and Emulsion Coatings By introducing sufficient carboxyl groups into a polymer, any type of resin can be made water soluble. These groups are then neutralized with a volatile base such as ammonia or an amine, rendering the resin a polymeric salt, soluble in water or water/ether–alcohol mixtures. The major disadvantage to such resins is that polymers designed to be dissolved in water will remain permanently sensitive to water. Because of this, they are not widely used industrially. However, water emulsions are widely accepted. The water-based latex emulsions are formulated with high molecular weight resins in the form of microscopically fine particles of high molecular weight copolymers of polyvinyl chloride, polyvinyl acetate, acrylic esters, stryren–butadiene, or other resins combined with pigments, plasticizers, UV stabilizers, and other ingredients. Water-based epoxy formulations are also available. The epoxy resin and a polyamide copolymer are emulsified and packaged in separate containers. After mixing, coalescence, and ultimate drying, the polyamide reacts with the epoxy to form the final film. The major advantage of the emulsion coatings is their ease of cleanup. Their disadvantage is the permanent water sensitivity of the coating, making them unsuitable for use in continually wet environments. Water-based coatings cannot be applied to blast-cleaned steel surfaces with the same confidence as solvent-based coatings. 7.13.1.1.9 Zinc-Rich Coatings In all of the above mentioned coatings, the final film properties of corrosion protection and environmental resistance have been attributed to organic composition of their constituent resin or binder. The pigment, although playing an important role in the final film properties, is secondary to the resistance of the organic binders.


Coatings

467

Conversely, in a zinc-rich coating, the role of the zinc pigment predominates. The high amount of zinc dust metal in the dried film determines the coating’s basic property, i.e., galvanic protection. For a coating to be considered zinc-rich, the common rule of thumb is that there must be at least 75% by weight of zinc dust in the dried film. This may change because conductive extenders (notably di-iron phosphide) have been added to improve weldability and burn-through, with supposedly equivalent protection at lower zinc loadings. The primary advantage of zinc-rich coatings is their ability to galvanically protect. The zinc coating preferentially sacrifices itself in the electrochemical corrosion reaction to protect the underlying steel. This galvanic reaction, together with the filling and sealing effect of zinc reaction products (primarily zinc carbonate, zinc hydroxide, and complex zinc salts), provides more effective corrosion protection to steel substrates than does any other type of coating. Zinc-rich coatings can not be used outside the pH range of 6–10.5. 7.13.1.2 Pigments Pigments serve several functions as part of the coating: They reinforce the film structurally, provide color and opacity, and serve special purposes for metal protection. Typical materials used as color or hiding pigments and to provide aesthetic value, retention of gloss and color, and to help with the film structure and impermeability are iron oxides, titanium dioxide, carbon or lamp black, and others. Pigments must be somewhat resistant to the environment and must be compatible with the resin. For example, calcium carbonate, that is attacked by acid, should not be used in an acid environment. Water-soluble salts are corrosion promoters, so special low salt containing pigments are used in primers for steel. Primers contain one of three kinds of pigments for special protective properties as follows: 1. Inert or chemically resistant. These are used to form barrier coatings in severe environments such as pH less than 5 or greater than 10. They are also used as nonreactive extender, hiding, or color pigments in neutral environments. 2. Active. Leads, chromates, or other inhibitive pigments are used in linseed oil/alkyd primers. 3. Galvanically sacrificial. Zinc is employed at high concentrations to obtain electrical contact for galvanic protection in environments between pH 5 and 10. Table 7.15 shows the type and characteristics of these pigments.


468


TABLE 7.15 Characteristics of Pigments for Metal Protective Paints Specific Gravity

Color

8.8

Orange

Fair

Basic silicon lead chromate

3.9

Orange

Poor

Zinc yellow (chromate)

3.3

Yellow

Fair

Zinc oxide (French process) Zinc dust at low concentration in coatings for steel

5.5

White

—

7.1

Gray

Good

7.1

Gray

Good

Makes electrical contact, galvanically sacrificial

Barrier pigments Quartz

2.6

Nil

Translucent

Mica Talc Asbestine Barytes Iron oxide Iron oxide Iron oxide black Titanium dioxide Carbon black

2.8 2.8 2.8 4.1 4.1 4.1 4.1 4.1 1.8

Nil Nil Nil Nil Red Ochre Black White Black

Translucent Translucent Translucent Translucent — — — Excellent Good

Inert, compatible with vinyl ester additives Impermeability and inertness Impermeability and inertness Impermeability and inertness Impermeability and inertness Impermeability and inertness Impermeability and inertness Impermeability and inertness Impermeability and inertness Impermeability and inertness

Pigment Active pigments Red lead

Galvanically protective pigments Zinc dust sacrificial at high concentration

Opacity

Specific Contribution to Corrosion Resistance Neutralizes film acids, insolubilizes sulfates and chlorides, renders water noncorrosive Neutralizes film acids, insolubilizes sulfates and chlorides, renders water noncorrosive Neutralizes film acids, anodic passivator, renders water noncorrosive Neutralizes film acids, renders water noncorosive Neutralizes film acids

Note: Titanium dioxide has better “hiding” than any other pigment. Source: From K.B. Tator. 1988. Coatings, in Corrosion and Corrosion Protection Handbook, P.A. Schweitzer, Ed., New York: Marcel Dekker, pp. 453–489.

7.13.1.3 Fillers (Extenders) In addition to lowering the cost, extenders also provide sag resistance to the liquid paint so that the edges remain covered. When the paint has dried, they reduce the permeability to water and oxygen and provide reinforcing structure within the film. Talc and mica are used extensively as extenders. Mica is limited to approximately 10% of the total pigment. Both talc and mica, but particularly mica, reduce the permeability through the film as platelike particles block permeation, forcing water and oxygen to seek a longer path through the binder around the particle.


Coatings

469

7.13.1.4 Additives Additives are used in coating formulations for specific purposes and in small, sometimes even trace amounts. Some typical additives and their purposes are as follows: Phenylmercury, zinc, cuprous compounds: mildew inhibitors Cobalt and manganese naphthanates: aid to surface and thorough drying Zinc oxide: protection of the resin from heat and sun Latex paints have a number of additives that act as stabilizers, coalescing aids, emulsion stabilizers, freeze–thaw stabilizers, and so on. 7.13.1.5 Solvents Organic solvents are usually required only to apply the coating and after application are designed to evaporate from the wet paint film. Water is considered either as a solvent or an emulsifier. The rate that solvents evaporate at influences the application characteristics of the coating. It is imperative that the solvent completely evaporate. If the solvents are partially retained and do not evaporate completely, premature failure by blistering or pinholing is likely to occur. Most coatings are formulated to be applied at ambient conditions of approximately 758F/248C and a 50% relative humidity. If ambient conditions are considerably higher or lower, it is conceivable that solvent release could pose a problem. This potential problem can be eased by changing the “solvent balance.” Generally, faster evaporating solvents should be used in colder weather, and slower evaporating solvents should be used in hot weather. Classes and characteristics of some common solvents are shown in Table 7.16. Low viscosity and two component epoxies and powder coatings are examples of paint systems referred to as solvent-free. The epoxy coatings may be mixed and applied without the use of a solvent, as the two components typically have a low viscosity. Powder coatings are cured by sintering. Before application thermoplastic powder coatings consist of a large number of small binder particles. These particles are deposited on a metal surface using special application techniques. Subsequently, the paint is baked in an oven to form a continuous film by sintering. 7.13.2 Surface Preparation For a paint to provide maximum protection, it is essential that the surface to which the paint is to be applied is properly prepared. The specific preparation system will be dependent on the coating system to be applied


a

Butyl acetateZ1.

Ester Alcohol Unsaturated aromatic Glycol Ethers

Ketone

Aromatic

Aliphatic

Class

313–316 168–172 167–178

0.95 0.90 0.79 0.90

High Intermediate Intermediate Intermediate High High

Cellosolve Butyl cellosolve

273–277 336–343

252–266

0.80

High

0.93 0.90

246–278 351–395 230–233 280–288 360–400 172–176

0.74 0.76 0.87 0.87 0.87 0.81

Nonpolar Nonpolar Intermediate Intermediate Intermediate High

VM&P naphtha Mineral spirits Toluene Xylene High solvency Methyl ethyl ketone (MEK) Methyl isobutyl ketone (MIBK) Cyclohexanone Ethyl acetate Ethanol Styrene

Polarity

Boiling Range (8F)

Solvent Name

Specific Gravity

Characteristics of Solvent Classes

TABLE 7.16

110 137

112 26 50

0.3 0.06

4.1 2.7 6.8

9.4

24.5 9.0 4.5 9.5 11.6 2.7

52 128 45 80 140 24 67

Evaporation Ratea

Flash Point of TCC

470 Corrosion of Linings and Coatings


Coatings

471

and should usually be in accord with one of the surface preparation specifications defined by the Steel Structures Painting Council that follow: Specification SP1: Solvent cleaning SP2: Hand-tool cleaning SP3: Power tool cleaning SP5: White-metal blast cleaning

SP6: Commercial blast cleaning SP7: Brush-off blast cleaning SP8: Pickling SP10: Near white blast cleaning

Description Removal of oil, grease, dirt, soil, salts and contaminants by cleaning with solvent, vapor, alkali, emulsion, or steam Removal of loose rust, mill scale, and paint, to degree specified, by hand chipping and wire brushing Removal of loose rust, mill scale, and paint, to degree specified, by power tool chipping, descaling, sanding, wire brushing, and grinding Removal of all visible rust, mill scale, paint, and foreign matter by blast cleaning, by wheel or nozzle, dry or wet, using sand, grit, or shot for very corrosive atmospheres where high cost of cleaning is warranted Blast cleaning until at least two-thirds of the surface area is tree of all visible residues (for severe exposure) Blast cleaning of all except tightly adhering residues of mill scale, rust and coatings, exposing numerous evenly distributed flecks of underlying metal Complete removal of rust and mill scale by acid pickling, duplex pickling, or electrolyte pickling Blast cleaning to near white metal cleanliness until at least 95% of the surface area is free of all visible residue (for high humidity, chemical atmosphere, marine, and other corrosive environments)

In addition to these mechanical methods, conversion coatings on metals produced by chemical or electrochemical means also increase the adhesive bonding of paint coatings. These types of coatings will be discussed later. The mechanical processes are used to remove dirt, rust, and mill scale from the surface and are adopted to steel products such as thick plates, construction steels, and steel structures that chemical processes are not available for. The chemical processes are applied to steel-strip products such as automotive bodies and home electrical appliances, to the internal coating of steel tubes, and to aluminum and zinc and their alloy products. 7.13.3 Application Methods The method of application for a corrosion resistant paint will depend on: 1. Purpose that coated product is to be used for 2. Environment that the coating will be exposed to


472


3. The type of paint 4. The shape and size of the object to be painted 5. The period of application process 6. Cost 7.13.3.1 Brushing This was once the main coating method, but at the present time, spray coating is more widely used. Brush coating has the following advantages: 1. Applicators are simple and inexpensive. 2. Complicated forms and shapes can be coated. 3. Thick films are obtained with one coat. 4. It provides particularly useful antirusting coating. The disadvantage of brushing results from the nonuniformity of coating layers, especially coating layers of rapidly drying paints. 7.13.3.2 Spray There are two types of spray coatings: air sprays and airless sprays. These coatings are subdivided into hot and cold types. 7.13.3.2.1 Air Spray Air spray is a process for spraying fine paint particles atomized by compressed air. Drying rates are high and a uniform and decorative surface is obtained. This method is used with paints that are not suitable for brushing methods, for mass produced painted products, or for products where surface appearance is important. 7.13.3.2.2 Airless Spray In an airless spray system, high pressure is supplied to the paint that is forced through a high pressure resistant hose and airless spray gun. High viscosity paints are warmed before spraying. This technique has the following advantages over the air spray system: 1. The sticking ratio of paint is increased to 25–40%. 2. Thicker films can be applied. 3. The running of paint on the object is reduced. Steel structures and bridge girders can be coated in the factory by this method because the efficiency of work is several times higher than brushing. However, its paint loss is 30–40% greater than for paints applied by brushing.


Coatings

473

7.13.3.3 Roller Coating This method is used to coat coils and sheets by passing them through two rollers. The thickness of paint film is controlled by adjusting the rollers. Oneside or both-sides coating is possible. 7.13.3.4 Powder Coating Because of the absence of organic solvents, powder coatings have grown in popularity as antipollution coatings. Coating thicknesses of 25–250 mm can be obtained. Automotive bodies, electric components, housing materials, wires, and cables make use of this method. Polyethylene and epoxy resins are the predominent types of paints used. At the present time, the following eleven procedures are used in this coating process: 1. Pouring method (flock coating) 2. Rotational coating of pipes 3. Fluidized bed 4. Dipping in nonfluidizing powders 5. Centrifugal casting 6. Rotational molding 7. Electrostatic Powder spraying 8. Electrostatic fluidized bed 9. Pouring or flowing of fluidized powder 10. Electrogasdynamics powder spraying 11. Flame spraying of thermoplastic powders

7.13.3.5 Electrodeposition The anodic deposition process for paint coating systems was introduced in the early 1960s and the cathodic deposition system in 1972. Electrodeposition processes are widely used since they possess the advantages of unmanned coating, automation, energy saving, and lower environmental pollution. This process is used to apply coatings to automotive bodies and parts, domestic electric components, machine parts, and architecturals such as window frames. Schematic illustrations of anodic and cathodic electrodeposition of paints are shown in Figure 7.22. The primary paints used in the electrodeposition process are anionic type resins with a carboxyl group (RCOOH, polybutadiene resin) and cationic type resin (R–NH2, epoxy resin). Hydrophilic groups and neutralizing agents are added to the water insoluble or undispersed prepolymers to convert them to soluble or dispersed materials. The dissolution of metal substrate in the cathodic process is much less than that in the anodic process. The primary resins used in the cathodic


H2O

OH− H+

Deposition of coating film


FIGURE 7.23 Electrodeposition of paints.

Deposition of film

2H2O

4H+ + O2 + 4e−

Anodic reactions

O2

(+)

Anodic

H2

(−)

2H+ + 2e−

O2 H2

+ 4e− + 2H2O

Cathodic reactions 4OH−

H2O

OH− H+

Deposition of coating film

4H+ + O2 + 4e−

H2 Deposition of film

2H2 + 2e−

Cathode reactions

2H2O

Anode reactions

O2

(+)

Cathodic

H2

(−)


Coatings

475

process are epoxy, and because epoxy resins provide good water and alkali resistance as well as adhesion, cationic paint coatings are superior in corrosion protection to anodic paint coatings. 7.13.3.6 Multilayer Coatings The protective ability of a coating is also dependent upon its thickness. Thicker coatings provide improved protection. However, single thick paint films tend to crack because of internal stress. When long term protection is required, multilayer paint coating systems are applied. The multilayer system to be used with a steel structure is determined by the required service life and the environmental conditions that the steel structure must exist under. General coating systems are applied to structures in mild environments, whereas, heavy-duty coating systems are applied to these structures in severe environments. Typical general coating systems and heavy duty coating systems are shown in Table 7.17 and Table 7.18, respectively. 7.13.4 Factors Affecting Life of Film For a paint film to perform effectively, it must have mechanical resistance to external forces and resistance against environmental factors. As discussed, a paint film is a composite layer that is composed of a vehicle (resin), pigment, and additives, and tends to contain defects in its structure. The common defects existing in a resultant paint film are: 1. Nonuniformity of vehicle molecules 2. Solvent residue 3. Residual stress TABLE 7.17 General Coating Multistage Paint Systems System Coat First Second Third Fourth Fifth Sixth

A Etching primer Oil corrosion Preventative paint Oil corrosion Preventative paint Long oil alkyd Resin paint Long oil alkyd Resin paint

B Etching primer Oil corrosion Preventative paint Oil corrosion Preventative paint Phenolic resin System MIO paint Chlorinated rubber System paint Chlorinated rubber System paint

C Zinc rich primer Chlorinated rubber System primer Chlorinated rubber System primer Chlorinated rubber System paint Chlorinated rubber System paint


476


TABLE 7.18 Heavy-Duty Coating Multilayer Paint Systems System Coat First

A

Second

Zinc spray or zinc-rich paint Etching primer

Third

Zinc chromate primer

Fourth

Phenolic resin system

Fifth

MIO paint Chlorinated rubber

Sixth

System Chlorinated rubber system paint

B Thick type zinc-rich paint Thick type Vinyl or chlorinated rubber system Thick type vinyl or chlorinated rubber system Vinyl resin or chlorinated Rubber system Vinyl resin or chlorinated Rubber system

C

D

Thick type zinc-rich paint Thick type epoxy primer

Zinc-rich primer Tar epoxy resin paint

Thick type epoxy primer

Tar epoxy resin paint

Epoxy resin system paint

Tar epoxy resin paint

Epoxy or polyurethane Resin system paint

4. Differences in expansion coefficients in multilayer coating systems 5. Poor adhesion of polymer to pigment 7.13.5 Strength of Paint Film Paint films require hardness, flexibility, brittleness resistance, abrasion resistance, mar resistance, and sag resistance, Paint coatings are formulated providing a balance of these mechanical properties. The mechanical strength of a paint film is described by the words hardness and plasticity that correspond to the modulus of elasticity and to the elongation at break obtained from the stress stress–strain curve of a paint film. Typical paint films have tensile properties as follows: Paints

Tensile Strength (g/mm)

Elongation at Break (%)

Linseed oil Alkyd resin varnish (16% PA) Amino-alkyd resin varnish (A/WZ7/3) NC lacquer Methyl-n-butyl-meta-acrylic resin

14–492 141–1266 2180–2602 844–2622 1758–2532

2–40 30–50 — 2–28 19–49

Mechanical properties of paint coatings vary depending on the type of pigment, baking temperatures, and aging times. As baking temperatures rise, the curing of paint films is promoted and elongation reduced. Tensile strength is improved by curing and the elongation at breaks is reduced with increased drying time.


Coatings

477 TABLE 7.19 Glass Transition Temperature of Organic Films Glass Transition Temperature, Tg (8C)

Organic Film Phthalic acid resin Acrylic lacquer Chlorinated rubber Bake type melamine resin Anionic resin Catonic resin Epoxy resin Tar epoxy resin Polyurethane resin Unsaturated polyester Acrylic powder paint

50 80–90 50 90–100 80 120 80 70 40–60 80–90 100

Structural defects in a paint film causes failures that are determined by environmental conditions such as thermal reaction, oxidation, photooxidation, and photothermal reaction. An important factor in controlling the physical properties of a paint film is the glass transition temperature Tg. In the temperature range higher than Tg, the motion of the resin molecules become more active so that hardness, plasticity, and the permeability of water and oxygen vary greatly. Table 7.19 lists the glass transition temperatures of organic films. Deterioration of paint films is promoted by photolysis, photooxidation, or photo thermal reaction as a result of exposure to natural light. Specifically, UV light (wavelength 40–400 nm) decomposes some polymer structures. Polymer films, such as vinyl chloride resins, are gradually decomposed by absorbing the energy of UV light. The Tg of a polymer is of critical importance in the photolysis process. Radicals formed by photolysis are trapped in the matrix, but they diffuse and react at higher temperatures than Tg. The principal chains of polymers with ketone groups form radicals: RCOR 0

R C COR 0

CO C R 0

ROCOR 0

OCOR 0

CO2 C R 0

The resultant radicals accelerate the degradation of the polymer and in some cases HCl (from polyvinyl chloride) or CH4 is produced. 7.13.6 Adhesion of Paint Film Paint coated materials are exposed primarily to the natural atmosphere. Consequently, paint adhesion is influenced by atmospheric factors,


478


particularly moisture and water. All organic polymers and organic coatings are permeable to water. They differ only in the degree of permeability. Table 7.13 provides typical values for the permeability and the diffusion coefficient for water in a number of different polymers. When moisture permeates into the paint substrate interface, blisters form. There are four mechanisms whereby blisters can form: 1. Volume expansion because of swelling 2. Gas inclusion or gas formation 3. Osmotic process because of soluble impurities at the film– substrate interface 4. Electroosmotic blistering Of the four mechanisms, osmotic blister formation is the most important. Past experience has indicated that 70% of all paint coating failures are the result of poor or inadequate surface preparation prior to application of the coating. Types of osmotically active surfaces at film-substrate interfaces are impurities such as sand particles from incomplete washing after wet sanding, water soluble salt residues from phosphating, or surface nests in a rust layer. It is also possible to entrap hydrophilic solvents to create blisters. Regardless of the specific driving force, the blister formation process is shown in Figure 7.24 using an example of an intact coating on steel. When the coating is exposed to an aqueous solution, water vapor molecules (and to a lesser extent, oxygen), diffuse into the film toward the coatingsubstrate interface. Eventually, water may accumulate at the interface forming a thin water film of at least several monolayers. The accumulation takes place at sites of poor adhesion or at sites where wet adhesion problems arise. The degree that permeated water may change the adhesion properties of a coated system to is referred to as wet adhesion. No initial, poorly adhered spots need be present for chemical disbondment to take place. A corrosion reaction can be initiated by the presence of an aqueous electrolyte with an electrochemical double layer, a cathodic species (oxygen) and an anodic species (metal). When the corrosion reaction has started at the interface, the corrosion products can be responsible for the buildup of osmotic pressure, resulting in the formation of macroscopic blisters (see Figure 7.24). Depending on the specific materials and circumstances, the blisters may grow out because of the hydrodynamic pressure in combination with one of the chemical propagation mechanisms such as cathodic delamination and anodic under-coating. Oxygen migration through a paint film coating is generally much lower than that of water. In some instances, the flow of oxygen increases with the water content of the film, probably because the water acts to swell the polymer.


Coatings H2O

479 O2

H2O

O2

H2O

H2O

OH

O2

–

H2O

OH

–

H2O

H2O

O2

H2O

H2O

O2

H2O

H2O

H2O

OH

Fe C

Permeation

C

A

O2

H2O

O2

2+ A

–

Fe

A

–

H2O

OH

Fe C

O2

OH

– Fe

C

2+ A

C

H2O

OH

–

C

Corrosion initiation

FIGURE 7.24 Introduction of a blister under an intact coating.

7.13.7 Types of Corrosion under Organic Coatings For corrosion to take place on a metal surface under a coating, it is necessary for an electrochemical double layer to be established. In order for this to take place, it is necessary for the adhesion between the substrate and coating to be broken. This permits a separate thin water layer to be formed at the interface from water that has permeated the coating. As previously mentioned, all organic coatings are permeable to water to some extent. Water permeation occurs under the influence of various driving forces: 1. A concentration gradient, e.g., during immersion or exposure to a humid atmosphere, resulting in true diffusion through the polymer 2. Capillary forces in the coating because of poor curing, improper solvent evaporation, entrapment of air during application, or bad interaction between binder and additives 3. Osmosis because of impurities or corrosion products at the interface between the metal and coating


480


Water molecules will eventually reach the coating substrate interface when a coated system has been exposed to an aqueous solution or a humid atmosphere. These molecules can interfere with the bonding between the coating and substrate, eventually resulting in the loss of adhesion and corrosion initiation if a cathodic reaction can take place. A constant supply of a cathodic species, such as water or oxygen, is required for the corrosion reaction to proceed. Water permeation may also result in the buildup of high osmotic pressure that are responsible for blistering and delamination. 7.13.7.1 Cathodic Delamination When cathodic protection is applied to a coated metal, loss of adhesion between the substrate and paint film, adjacent to defects, often takes place. This loss of adhesion is known as cathodic delamination. Such delamination may also occur in the absence of applied potential. Separation of anodic and cathodic reaction sites under the coating results in the same local driving force as during external polarization. The propagation of a blister because of cathodic delamination under an undamaged coating on a steel substrate is schematically illustrated in Figure 7.25. Under an intact coating, corrosion may be initiated locally at sites of poor adhesion. A similar situation develops in the case of corrosion under a defective coating. When there is a small defect in the coating, part of the substrate is directly exposed to the corrosive environment. Corrosion products are formed immediately that block the damaged site from oxygen. The defect in the coating is sealed by the corrosion products, after which corrosion propagation takes place, according to the same mechanism as for the initially undamaged coating. Refer to Figure 7.25 for the sequence of events. 7.13.7.2 Anodic Undermining Anodic undermining results from the loss of adhesion caused by anodic dissolution of the substrate metal or its oxide. In contrast to cathodic delamination, the metal is anodic at the blister edges. Coating defects may cause anodic undermining, but in most cases it is associated with a corrosion sensitive site under the coating, such as a particle from a cleaning or blasting procedure, or a site on the metal surface with potentially increased corrosion activity (scratches). These sites become active once the corrodent has penetrated to the metal surface. The initial corrosion rate is low. However, an osmotic pressure is caused by the soluble corrosion products which stimulates blister growth. Once formed, the blister will grow because of a type of anodic crevice corrosion at the edge of the blister. Coated aluminum is very sensitive to anodic undermining, whereas, steel is more sensitive to cathodic delamination.


Coatings

481 H2O

O2

H2O

O2

H2O

O2

H2O

Corrosion initiation H2O

O2

H2O

Blocking of pore O2

H2O

C

H2O

anodic

H2O

O2

C

Cathodic delamination FIGURE 7.25 Blister initiation and propagation under a defective coating (cathodic delamination).

7.13.7.3 Filiform Corrosion Metals with semipermeable coatings or films may undergo a type of corrosion, resulting in numerous meandering threadlike filaments of corrosion beneath the coatings or films. Conditions that promote this type of corrosion are: 1. High relative humidity (60–95% at room temperature). 2. The coating is permeable to water. 3. Contaminants (salts, etc.) are present on or in the coating or at the coating-substrate interface.


482


4. The coating has defects (mechanical damage, pores, insufficient coverage of localized areas, air bubbles). Filiform corrosion under organic coatings is common on steel, aluminum, magnesium, and zinc (galvanized steel). It has also been observed under electroplated silver plate, gold plate, and under phosphate coatings. This form of corrosion is more prevalent under organic coatings on aluminum than on other metallic surfaces, being a special form of anodic undermining. A differential aeration cell is the basic driving force. The filaments have considerable length but little width and depth and consist of two parts: a head and a tail. The primary corrosion reactions and, subsequently, the delamination process of the paint film takes place in the active head, whereas, the tail is filled with the resulting corrosion products. As the head of the filiform moves, the filiform grows in length.

7.13.8 Causes of Coating Failures Coating failures result from two basic causes: 1. Poor or inadequate surface preparation and/or application of the paint to the substrate 2. Atmospheric effects Coating failures typical from surface preparation and application problems include: 1. Cracking, checking, and alligatoring. These type of failures develop with the aging of the paint film. Shrinkage within the film during aging causes cracking and checking. Alligatoring is a film rupture, usually caused by application of a hard brittle film over a more flexible film. 2. Peeling, flaking, and delamination. These failures are caused by poor adhesion. When peeling or flaking occurs between coats, it is called delamination. 3. Rusting. Failure of a coated surface may appear as (a) spot rusting at minute areas, (b) pinhole rusting at minute areas, (c) rust nodules breaking through the coating, and (d) underfilm rusting, that eventually causes peeling and flaking of the coating. 4. Lifting and wrinkling. When the solvent of a succeeding coat of paint too rapidly softens the previous coat, lifting results. Rapid surface drying of a coating without uniform drying throughout the rest of the film results in a phenomenon known as wrinkling.


Coatings

483

5. Failures around weld areas. Coating adhesion can be hampered by weld flux that may also accelerate corrosion under the film. Relatively large projections of weld spatter cause possible gaps and cavities that may not be coated sufficiently to provide protection. 6. Edge failures. Edge failures usually take the form of rusting through the film at the edge where the coating is normally the thinnest. This is usually followed by eventual rust creepage under the film. 7. Pinholing, tiny holes that expose the substrate, caused by improper paint spray atomization or segregation of resin in the coating. If practical during application, brush out coating. After application and proper cure, apply additional coating. Polymer coatings are exposed to the environment and, therefore, are subject to degradation by environmental constituents. The primary factors promoting degradation are thermal, mechanical, radiant, and chemical. Polymers may also be degraded by living organisms such as mildew. Any atmospheric environment is subject to dry and wet cycles. Since water and moisture have a decided effect on the degradation of a coating, the time of wetness of a coating is important. Moisture and water that attack organic films are from rain, fog, dew, snow, and water vapors in the atmosphere. Relative humidity is a particularly important factor. As exposure time is increased in 100% relative humidity, the bond strength of a paint coating is reduced. This is shown in Table 7.20. Temperature fluctuations and longer time of wetness tends to produce clustered water that increases the acceleration of degradation of the organic film, particularly in a marine atmosphere. The most severe natural atmosphere for a paint film is that of a seashore environment. The mode of degradation may involve depolymerization, generally caused by heating, splitting out of constituents in the polymer, chain scission, cross-linking, oxidation, and hydrolysis. Polymers are subject to cracking on the application of a tensile force, particularly when exposed to

TABLE 7.20 Relationship of Bond Strength to Exposure Time in 100% Relative Humidity Bond Strength (psi) Exposure Time (h) Initial 24 48 120 195 500

Epoxy Ester

Polyurethane

Thermosetting Acrylic

4790 1640 1500 — 1400 1390

3410 1500 1430 1390 1130 670

5700 3650 3420 2400 1850 480


484


certain liquid environments. This phenomenon is known as environmental stress cracking or stress corrosion cracking. Other factors in the atmosphere that cause corrosion or degradation of the coating are UV light, temperature, oxygen, ozone, pollutants, and wind. Types of failures caused by these factors are: 1. Chalking. UV light, moisture, oxygen, and chemicals degrade the coating resulting in chalk. This may be corrected by providing an additional top coat of material with proper UV inhibitor. 2. Color fading or color change. This may be caused by chalk on the surface or by breakdown of the colored pigments. Pigments can be decomposed or degraded by UV light or reaction with chemicals. 3. Blistering. Blistering may be caused by: a. Inadequate release of solvent during both application and drying of the coating system. b. Moisture vapor that passes through the film and condenses at a point of low adhesion. c. Poor surface preparation. d. Poor adhesion of the coating to the substrate or poor intercoat adhesion. e. A coat within the paint system that is not resistant to the environment. f. Application of a relatively fast drying coating over a relatively porous surface. g. Failures because of chemical or solvent attack. When a coating is not resistant to its chemical or solvent environment, there is apparent disintegration of the film. 4. Erosion, coating worn away. Loss of coating because of inadequate erosion protection. Provide material with greater resistance to erosion. 7.13.9 Maintenance of the Coating Any paint job, even if properly done, does not last forever. Within the first six months or year after application, spots, inadvertent misses, or weak spots in the coating system can be detected by simple visual inspection. A thorough inspection and repair should be done at this time. Over a period of time, the coating will break down and deteriorate as a result of the effect of the environment. Scheduled inspections should he made to determine the extent and rate of the coating breakdown. Spot touchup repair should be made at localized areas of failure before deterioration of the entire coated surface has taken place. Extensive costs of total surface preparation (such as complete blast cleaning removal of all old coating) can be avoided if a “planned


Coatings

485

maintenance approach” of periodic spot touchup and an occasional recoat of the entire surface is followed. Many coatings that provide good long term protection are more difficult to touch up or repair in the event of physical damage or localized failure. This is particularly true of the thermosetting and zinc-rich coatings. Application of a subsequently applied paint coat to an older aged epoxy, urethane, or other catalyzed coating often results in reduced adhesion that leads to peeling. Thermoplastic coatings do not normally present this problem. Solvents of a freshly applied thermoplastic coating soften and allow for intermolecular mixing of the new and old coatings with good intercoat adhesion. Heavily pigmented coatings, such as zinc-rich, require agitated pots to keep the pigment in suspension during application. Because of this, touchup and repair of large areas is not recommended using zinc-rich coatings unless it is done by spray using an agitated pot. For the most part, oil-based coatings (alkyds, epoxy esters, and modifications thereof) have a greater tolerance for poor surface preparation and an ability to wet, penetrate, and adhere to poorly prepared surfaces or old coatings. Consequently, these coatings are often specified for these purposes, even though they do not provide as long a term of corrosion protection.

References 1. 2. 3. 4. 5. 6. 7. 8.

I. Suzuki. 1989. Corrosion Resistant Coatings Technology, New York: Marcel Dekker. D. Satas. 1991. Coatings Technology Handbook, New York: Marcel Dekker. F. Mansfield. 1987. Corrosion Mechanisms, New York: Marcel Dekker. F.C. Porter. 1994. Corrosion Resistance of Zinc and Zinc Alloys, New York: Marcel Dekker. P.A. Schweitzer. 1988. Corrosion and Corrosion Protection Handbook, 2nd ed., New York: Marcel Dekker. H.R. Copson. 1995. Report of subcommittee B-3 on Atmospheric Corrosion of Nonferrous metals. ASIM Annual Meeting, Atlantic City, NJ, June 25. R. Leidheiser, Jr. 1987. Coatings, in Corrosion Mechanisms, F. Mansfield, Ed., New York: Marcel Dekker, pp. 165–209. K.B. Tator. 1988. Coatings, in Corrosion and Corrosion Protection Handbook, 2nd ed., P.A. Schweitzer, Ed., New York: Marcel Dekker, pp. 453–489.


8 Specific Organic Coatings

To select a suitable coating system, it is necessary to determine the environmental conditions around the structure to be painted. If the coating is to be applied to an exterior surface, are there nearby chemical plants, pulp and paper mills, or heavy industries that might provide airborne pollutants? Is the objective of the coating to provide an aesthetic appearance or to provide maximum corrosion protection that will limit the colors to the normal grays, whites, and pastels of the most corrosion resistant coatings? Will the surface be predominantly wet (salt or freshwater) or exposed to a chemical contaminant (acid or alkaline)? Is the environment predominantly a weathering environment subject to heat, cold, daily or seasonal temperature changes, precipitation, wind (flexing), exposure to sunlight, or detrimental solar rays? Will the surface be exposed to occasional spells of a corrosive or solvent? After the environmental conditions of the area have been defined, a suitable resistant coating can be selected. Characteristics, corrosion resistance, limitations, and uses of the common generic types of coatings will be discussed.

8.1 Thermoplastic Resins Protective coatings formulated from these resins do not undergo any chemical change from the time of application until the final properties of a dried protective film have been attained. The film is formed by the evaporation of the solvent, concentrating the binder/pigment solution and causing it to precipitate as a continuous protective film. 8.1.1 Vinyls These are polyvinyls dissolved in aromatics, ketones, or esters. 1. Resistance: Insoluble in oils, greases, aliphatic hydrocarbons, and alcohols; resistant to water and salt solutions; at room temperature, resistant to inorganic acids and alkalies; fire resistant.

487


488


2. Temperature resistance: 1808F/828C dry; 1408F/608C wet. 3. Limitations: Dissolved by ketones, aromatics, and ester solvents. Adhesion may be poor until all solvents have vaporized from the coating. Relatively low thickness per coat requiring several coats to provide adequate protection. 4. Features: Tasteless and odorless. 5. Applications: Used on surfaces exposed to potable water, as well as for immersion service, sanitary equipment, and widely used as industrial coatings. When used for immersion service, it is essential that all solvents have evaporated before placing the vinyl coated object into service. The high polarity of the resin tends to retain the solvents used to dissolve the resin. Solvent evaporation is retarded, with the resultant effect of solvent voids within the coating, pinholes caused by volatilization of retained solvents upon heating or water filled blisters because of hydrogen bonding attraction of water by the retained solvents in the coating. 8.1.2 Chlorinated Rubber Chlorinated rubber resins include those resins produced by the chlorination of both natural and synthetic rubbers. Chlorine is added to unsaturated double bonds until the final product contains approximately 65% chlorine. A plastisizer must be added because the final product is a hard, brittle material with poor adhesion and elasticity. The volume of solids of the coating dissolved in hydrocarbon solvents is somewhat higher than that of a vinyl; therefore, a suitably protective chlorinated rubber system often consists of only three coats. 1. Resistance: Chemically resistant to acids and alkalies; low permeability to water vapor; abrasion resistant; fire resistant. Nontoxic. 2. Temperature resistance: 2008F/938C dry; 1208F/498C wet. 3. Limitations: Degraded by ultraviolet light; attacked by hydrocarbons. 4. Applications: Excellent adherence to concrete and masonry. Used on structures exposed to water and marine atmospheres (swimming pools, etc.). When used for water immersion service, the same care must be exercised during evaporation as was described for the vinyls. 8.1.3 Acrylics The acrylics can be formulated as thermoplastic resins, thermosetting resins, and as a water emulsion latex.


Specific Organic Coatings

489

TABLE 8.1 Glass Transition Temperature vs. Application Area Tg (8C/8F) 80–100/176–212 50–65/122–149 35–50/95–122 10–40/50–100

Application Area High heat resistant coatings Floor care coatings General industrial coatings Decorative paints

The resins are formed from polymers of acrylate esters, primarily polymethyl methacrylate and polyethyl acrylate. Because the acrylate esters do not contain tertiary hydrogens attached directly to the polymer backbone chain, they are exceptionally stable to oxygen and UV light. A wide range of monomers is available for use in designing a specific acrylic system. Typically, mixtures of monomers are chosen for the properties they impart to the polymer. The glass transition temperature Tg of the polymer can be varied by selection of the proper monomers. This permits a varied area of application. Table 8.1 illustrates the wide range of Tg resulting from different monomer compositions for emulsion acrylics. Acrylics may be formulated as lacquers, enamels, and emulsions. Lacquers and baking enamels are used as automotive and appliance finishes. In both these industries, acrylics are used as top coats in multicoat finishing systems. 1. Resistance: Somewhat resistant to acids, bases, weak and moderately strong oxidizing agents, and many corrosive industrial gases and fumes. Resistant to weather and UV light. 2. Limitations: Limited penetrating power (water emulsion) because of water surface tension; may flash rust as a primer over bare steel; not suitable for immersion service or strong chemical environments. Soluble in ketones, esters, aliphatic chlorinated hydrocarbons, and aromatic hydrocarbons. 3. Application: Compatible with other resins and used to improve application, lightfastness, gloss, or color retention. Used in automotive and appliance finishes.

8.2 Thermosetting Resins After application and solvent evaporation of a thermosetting resin, a chemical change takes place. As this chemical reaction is taking place, the coating is said to be “curing.” This reaction may take place at room


490


temperature or in baked coatings at elevated temperatures. The reaction is irreversible. Exposure to high temperature or to solvents does not cause the coating to soften or melt. 8.2.1 Epoxy Epoxy resins on their own are not suitable for protective coatings because when pigmented and applied, they dry to a hard, brittle film with very poor chemical resistance. By copolymerizing with other resins, the epoxy resins will form a durable protective coating. 8.2.2 Polyamine Epoxy 1. Resistance: Resistant to acids, acid salts, alkalies, and organic solvents. 2. Temperature resistance: 2258F/1078C dry; l908F/888C wet. 3. Limitations: Not resistant to UV light, harder and less flexible than other epoxies; less tolerant of moisture during application. 4. Applications: Widest range of chemical and solvent resistance of epoxies; used for piping and vessels. 8.2.3 Polyamide Epoxy 1. Resistance: Resistance inferior to that of polyamine epoxy; only partially resistant to acids, acid salts, alkalies, and organic solvents; resistant to moisture. 2. Temperature resistance: 2258F/1088C dry; 1508F/668C wet. 3. Limitations: Not resistant to UV light; inferior chemical resistance. 4. Applications: Used on wet surfaces under water, as in tidal zone areas of pilings, oil rigs, etc. 8.2.4 Aliphatic Polyamine 1. Resistance: Partially resistant to acids, acid salts, and organic solvents. 2. Temperature resistance: 2258F/1088C dry; 1508F/668C wet. 3. Limitations: Film formed has greater permeability than other epoxies. 4. Application: Used for protection against mild atmospheric corrosion. 8.2.5 Esters of Epoxies and Fatty Acids 1. Resistance: Resistant to weathering and UV light. 2. Temperature resistance: 2258F/1088C dry; 1508F/668C wet.



491

3. Limitations: Chemical resistance generally poor. 4. Applications: Used where the properties of a high quality oil base paint are required. 8.2.6 Coal Tar Plus Epoxy 1. Resistance: Excellent resistance to freshwater, saltwater, and inorganic acids. 2. Temperature resistance: 2258F/1088C dry; 1508F/668C wet. 3. Limitations: Not resistant to weather and sunlight; attacked by organic solvents. 4. Applications: Used on clean blasted steel for immersion service or below grade service. 8.2.7 Urethanes Polyurethane-resin based coatings are versatile. They are available as oil modified, moisture curing, blocked, two component, and lacquers. Properties of the various types are shown in Table 8.2. The urethane coatings possess excellent gloss and color retention and are used as a decorative coating of tank cars and steel in highly corrosive environments. Moisture cured types require humidity during application and may yellow under UV light. They have a temperature resistance of 2508F/1218C dry; 1508F/ 668C wet. Catalyzed (two component) urethanes exhibit very good chemical resistance. They are not recommended for immersion or exposure to strong TABLE 8.2 Properties of Polyurethane Coatings One-Component Property

Urethane Oil

Moisture

Blocked

Abrasion resistance Hardness Flexibility Impact resistance Solvent resistance Chemical resistance Corrosion resistance Adhesion Toughness Elongation Tensile Cure rate Cure temperature

Fair–good Medium Fair–good Good Fair Fair Fair Good Good Poor Fair Slow Room

Excellent Medium–hard Good–excellent Excellent Poor–fair Fair Fair Fair–good Excellent Poor Good Slow Room

Good–excellent Medium–hard Good Good–excellent Good Good Good Fair Good Poor Fair–good Fast 300–3908F 149–1998C

TwoComponent Excellent Soft–very hard Good–excellent Excellent Excellent Excellent Excellent Excellent Excellent Excellent Good–excellent Fast 2128F/1008C


Lacquer Fair Soft–medium Excellent Excellent Poor Fair–good Good–excellent Fair–good Good–excellent Excellent Excellent None 150–2258F 66–1088C

492


acids/alkalies. They have a temperature resistance of 2258F/1088C dry; 1508F/668C wet. These resins are quite expensive. 8.2.8 Polyesters In the coating industry, polyesters are characterized by resins based on components that introduce unsaturation (–CaC–) directly into the polymer backbone. The most common polyester resins are polymerization products of maleic or isophthalic anhydride or their acids. In producing paint, the polyester resin is dissolved in styrene monomer, together with pigment and small amounts of inhibitor. A free radical initiator, commonly a peroxide, and additional styrene are packaged in another container. When applied, the containers are mixed. Sometimes, because of the fast initiating reaction (short pot life), they are mixed in an externally mixing or dualheaded spray gun. After being mixed and applied, a relatively fast reaction takes place, resulting in cross-linking and polymerization of the monomeric styrene with the polyester resin. Polyester coatings exhibit high shrinkage after application. The effect of high shrinkage can be reduced by proper pigmentation that reinforces the coating and reduces the effect of the shrinkage. 1. Resistance: Excellent resistance to acids and aliphatic solvents; good resistance to weathering. 2. Temperature resistance: 1808F/828C dry and wet. 3. Limitations: Not suitable for use with alkalies and most aromatic solvents because they swell and soften these coatings. They also have a short pot life and must be applied with special equipment. 4. Applications: Coatings for tanks and chemical process equipment. 8.2.9 Vinyl Esters The vinyl esters are formulated in a manner similar to the polyesters. They are derived from a resin based on a reactive end vinyl group that can open and polymerize. The vinyl esters have better moisture and chemical resistance than the polyesters. They also have good resistance to weathering and acids.

8.3 Autooxidative Cross-Linking Paints Paints of this type rely on the reaction of a drying oil with oxygen to introduce cross-linking within the resin and attainment of final film properties. The final coating is formed when a drying oil reacts with a resin that is



493

then combined with pigments and solvents. These paints are packaged in a single can. The can is opened, the paint mixed and applied. As the solvents evaporate, the coating becomes hard. Since oxygen in the atmosphere reacts with the coating to produce additional cross-linking, the final film properties may be formed weeks or months after application. Among these resin fortified “oil based paints” are included the alkyds, epoxy esters, oil modified urethanes, etc. These paints may be formulated as air-drying or baking types, and with suitable pigments, can be formulated to be resistant to a variety of moisture and chemical fume environments as well as application over wood, metal, and masonry substrates. These paints have the following advantages: Ease of application Excellent adhesion Relatively good environmental resistance Tolerance for poorer surface preparation Their major disadvantages are: Cannot be used for immersion or in areas of high chemical fume concentration Reduced moisture and chemical resistance compared to other resin coatings 8.3.1 Epoxy Esters Esters of epoxies and fatty acids modified. 1. Resistance: Resistant to weathering; limited resistance to chemicals and solvents. 2. Temperature resistance: 2258F/1088C dry; 1508F/668C wet. 3. Limitations: Attacked by alkalies. Application time between coats is critical. 4. Applications: Used where the properties of a high quality oil based paint is required. 8.3.2 Alkyd Resin These paints are the most widely used synthetic resins. They are produced by reactions of phthalic acid with polyhydric alcohols such as glycerol and vegetable oil (or fatty acid). Classification is by oil content into drying types and baking types. Drying types provide good weathering resistance and good adhesion to a wide variety of substrates, but relatively poor resistance


494


to chemical attack. They have a maximum temperature resistance of 2258F/1088C dry; 1508F/668C wet. These paints are used on exterior wood surfaces for primers requiring penetrability and in less severe chemical environments. 8.3.3 Oil-Based Paints These paints are mixtures of pigment and boiled linseed oil or soybean oil or other similar materials. This paint is used as a ready-mixed paint particularly on wood surfaces because of its penetrating power. It is resistant to weather, but has relatively poor chemical resistance and will be attacked by alkalies. Temperature limitations are 2258F/1088C dry; 1508F/668C wet. 8.3.4 Water Emulsion Paints Water-based latex emulsions consist of fine particles of high molecular weight copolymers of polyvinyl chloride or polyvinyl acetate, acrylic esters, styrene–butadiene, or other resins combined with pigments, plasticizers, UV stabilizers, and other ingredients. A variety of thickeners, coalescing aids, and other additives are present in the water phase. The paint film is formed by water evaporation. Initial adhesion may be relatively poor as the water continues to evaporate, and coalescing aids, solvents, and surfactants evaporate or are leached from the “curing” film. Final adhesion and environmental resistant properties are reached from as little as a few days to a few months after application. 1. Resistance: Resistant to weather but poor chemical resistance. 2. Temperature resistance: 1508F/668C dry or wet. 3. Limitations: Not suitable for immersion service. 4. Applications: Used in general decorative applications on wood. 8.3.5 Silicones There are two types: high temperature and water repellent in water or solvent. 1. Resistance: Excellent resistance to sunlight and weathering; poor resistance to acids and alkalies; resistant to water. 2. Temperature resistance: In aluminum formulation, resistant to 12008F/6998C and to weathering at lower temperatures. 3. Limitations: High temperature type requires baking for good cure; not chemically resistant. 4. Applications: Used on surfaces exposed to high temperatures as water repellant; water solvent formulations used on limestone,



495

cement, and nonsilaceous materials; solvent formulations used oil bricks and noncalcareous masonry.

8.4 Bituminous Paints There are two paints in this category: asphalt and coal tar. 8.4.1 Asphalt Paint Asphalt paint consists of solids from crude oil refining suspended in aliphatic solvents. 1. Resistance: Good moisture resistance; good resistance to weak acids, alkalies, and salts; better weathering properties than coal tar. 2. Temperature resistance: Softens at 1008F/388C. 3. Limitations: Heavy, dark color hides corrosion under coating. 4. Applications: Used in above-ground weathering environments and chemical fume atmospheres. 8.4.2 Coal Tar Coal tar is a distilled coking by-product in an aromatic solvent. 1. Resistance: Excellent resistance to moisture; good resistance to weak acids and alkalies, petroleum oils, and salts. 2. Temperature resistance: Will soften at 1008F/388C. 3. Limitations: Will be degraded by exposure to UV light and weathering. 4. Applications: Used on submerged or buried steel and concrete.

8.5 Zinc-Rich Paints Zinc-rich paints owe their protection to galvanic action. Whereas all of the preceding coatings owe their final film properties, corrosion resistance, and environmental resistance to the composition of their resin or binder rather than their pigment, the high amount of zinc dust metal pigment in zinc-rich paints determines the coating’s fundamental property: galvanic protection. Many of the previous coatings, chlorinated rubber and epoxies in particular,


496


are formulated as zinc-rich coatings. In doing so, the high pigment content changes the properties of the formulated coating. Zinc-rich coatings can be classified as organic or inorganic. The organic zinc-riches have organic binders with polyamide epoxies and chlorinated rubber binders being the most common. Other types such as urethane zinc-rich are also available. These latter coatings are more easily applied than the other zinc-rich coatings. Inorganic zinc-rich binders are based on silicate solutions that after drying or curing, crystallize and form an inorganic matrix, holding zinc dust particles together and to the steel substrate. For a coating to be considered zinc-rich, it must contain at least 75% by weight of zinc dust in the dry film. This may change because conductive extenders (notably di-iron phosphite) have been added to improve weldability and burn-through with supposedly equivalent protection at lower zinc loadings. The primary advantage of zinc-rich coatings is their ability to galvanically protect. The zinc pigment in the coating preferentially sacrifices itself in the electrochemical corrosion reaction to protect the underlying steel. This galvanic reaction, together with the filling and sealing effect of zinc reaction products (primarily zinc carbonate, zinc hydroxide, and complex zinc salts), provides more effective corrosion protection to steel substrates than does any other type of coating. Zinc-rich coatings cannot be used outside the pH range of 6–10.5. Table 8.3 presents a summary of the properties of various paint formulations.

8.6 Selecting a Paint System The first step in selecting a paint system for corrosion protection is to determine the environment around the structure or item to be painted. Is the environment predominantly a weathering environment subject to heat, cold, daily or seasonal temperature changes, precipitation, wind (flexing), exposure to sunlight, or detrimental solar rays? If the structure or item is located outdoors, are there chemical plants located nearby, or pulp and paper mills, or other industrial facilities that are apt to discharge airborne pollutants? Is color, gloss, and overall pleasing effect more important than corrosion protection, or are the normal grays, whites, and pastels of the more corrosion resistant paints satisfactory? If located in a chemical facility, what specific chemicals are used nearby; is there any chance of a chemical spill on the painted surface? Since surface preparation is an important factor in the selection of a paint system, the suitability or availability of the surface for specific preparation techniques must be known. In some instances, certain types of surface preparation may not be permitted or practical. For example, many companies



R

R R

Urethanes catalyzed R

R

N

N R

PR PR

R

R

Oil-based coatings with vehicle (alkyd epoxy, urethane) Urethane, moisture cured

PR N

PR

N

Polyamide plus epoxy resin (polyamide epoxy) Aliphatic polyamine Esters of epoxies and fatty acids (epoxy esters) Coal tar plus epoxy resin

Weak R R

R

PR

PR

N

Epoxies, polyamine plus epoxy resin

Weak R R

N

PR

R

R

R

Alkali

N

Acid

Chlorinated rubbers dissolved in hydrocarbon solvents

Weather R

UV

Resistance To

Vinyls dissolved in esters, aromatics, or ketones

Coating Type

Properties of Paints

TABLE 8.3

R

R

R

R

R

R

R

Moisture

R

PR PR

PR

PR

R

Salt Solutions

(continued )

Adhesion may be poor until all solvents have vaporized from the coating Excellent adhesion to metals, concrete, and masonry. Used on structures exposed to water and marine atmospheres Harder and less flexible than other epoxies. Greatest chemical resistance of the epoxies Chemical resistance inferior to that of the polyamine epoxies Flexible film On surfaces requiring the properties of a high quality oil based paint Used on clean blast cleaned steel for immersion or below grade service. Attacked by organic solvents Lower cost than most coatings. Used on exterior wood surfaces May yellow under UV light. High gloss and ease of cleaning Expensive. Used as coating on steel in highly corrosive areas

Comments

Specific Organic Coatings 497


R R

Note: R, resistant; N, not resistant; PR, poor resistance.

Zinc-rich metallic zinc in an organic or inorganic vehicle Acrylic-resin water emulsion base

R

N

N R

R

R

PR

Asphalt. Solids from crude oil refining in aliphatic solvents

N

R

R

Weak R

Weak R Weak R

N

R

R

R

R

R

Moisture

Weak R

Salt Solutions

Weak R

Provides galvanic protection as a primer

Weak R Weak R

N

N

N

Alkali

Resistance To Acid

Silicones, water repellent in water or solvent Silicones, water based aqueous emulsions of polyvinyl acetate, acrylic or styrene– butadiene latex Polyesters, organic acids combined with polybasic alcohols. Styrene is a reaction diluent Coal tar

Weather

UV

Coating Type

TABLE 8.3 Continued

Limited penetrating power. May flash rust as a primer over bare steel. Not suitable for immersion service. Soluble in ketones, esters, aliphatic chlorinated hydrocarbons, and aromatic hydrocarbons

Used in above ground weathering environments and chemical fume atmospheres

Must be applied with special equipment. Not suitable for use with most aromatic solvents Used on submerged or buried steel

May flash rust as a primer on steel. Not chemically resistant

Used on masonry surfaces

Comments



499

do not permit open blast cleaning where there is a prevalence of electric motors or hydraulic equipment. Refineries, in general, do not permit open blast cleaning or any other method of surface preparation that might result in the possibility of a spark, static electricity buildup, or an explosion hazard. If a new facility is being constructed, it is possible that during erection many areas may become enclosed or covered or so positioned that access is difficult or impossible. These structures must be painted prior to installation. When all of this information has been collected, the appropriate paint systems may be selected. In most instances, it will not be practical or possible to select one single coating system for the entire plant. There will be areas requiring systems to provide protection from aggressive chemicals, whereas, other areas may require coating systems simply for esthetics. If an area is a combination of mild and aggressive conditions, a coating system should be selected that will be resistant to the most aggressive condition. Several typical industrial environmental areas have been illustrated that coating systems may be exposed to with recommendations for paint systems to be used in these areas. The paint systems are shown in Table 8.4 through Table 8.9 with the appropriate surface preparation. The tables have been arranged based on surface preparation. Each coating system shown in a particular table requires the same surface preparation. 8.6.1 Area 1. Mild Exposure This is an area where structural steel is embedded in concrete, encased in masonry, or protected by noncorrosive type fireproofing. In many instances, no coating will be applied to the steel. However, it is a good idea to coat the steel substrate with a protective coating to protect them during construction and in case they end up being either intentionally or unintentionally exposed. A good practice would be to apply a general use epoxy primer 3–5 mils dry film thickness (dft) (75–125 mm). If the surface cannot be abrasive blasted, a surface tolerant epoxy mastic may be used. Recommended systems are found in Table 8.7 systems A and C. 8.6.2 Area 2. Temporary Protection; Normally Dry Interiors This area consists of office space or dry storage areas (warehouses) or other locations exposed to generally mild conditions or areas where oil-based paints presently last for ten or more years. If located in an industrial environment, there is the possibility of exposure to occasional fumes, splashing, or spillage of corrosive materials. Because of this, it is suggested that an industrial grade acrylic coating system or a single coat of epoxy be applied. This recommendation is not suitable for interior surfaces that are frequently cleaned or exposed to steam cleaning. Refer to area 4. Recommended for this area are systems A and C in Table 8.7.


500


TABLE 8.4 Multilayer Paint Systems Requiring Commercial Blast (SSPC-SP-6) for Surface Preparation System A. Inorganic Zinc/Epoxy Mastic Paint layers One coat inorganic zinc: 2–3 mils dft (50–75 mm) One coat epoxy mastic: 4–6 mils dft (100–150 mm) Properties Zinc primer provides outstanding corrosion resistance and undercutting resistance. A barrier protection for the zinc primer is provided by the finish coat of epoxy which also provides a color coat for appearance. Suitable for use on carbon steel only Limitations A relatively high level of applicator competence required for the primer System B. Inorganic Zinc/Epoxy Primer/Polyurethane Finish Paint layers One coat inorganic zinc: 2–3 mils dft (50–75 mm) One coat epoxy primer: 4–6 mils dft (100–150 mm) One coat polyurethane finish: 2–4 mils dft (50–100 mm) Properties Zinc primer provides outstanding corrosion resistance and undercutting resistance. The zinc primer is protected by a barrier coating of epoxy primer, while the finish coat of polyurethane provides color and gloss retention. This is a premium industrial finish for steel surfaces. Can only be used on carbon steel Limitations A relatively high level of applicator competence required for the primer System C. Inorganic Zinc/Acrylic Finish Paint layers One coat inorganic zinc: 2–3 mils dft (50–75 mm) One coat acrylic finish: 2–3 mils dft (50–75 mm) Properties Zinc primer provides outstanding corrosion resistance and undercutting resistance. Water based single package finish has excellent weathering and semigloss appearance Limitations A relatively high level of applicator competence required for the primer. The finish coat has low temperature curing restrictions System D. Aluminum Epoxy Mastic/Epoxy Finish Paint layers One coat aluminum epoxy mastic: 4–6 mils dft (100–150 mm) One coat epoxy finish: 4–6 mils dft (100–150 mm) Properties Can be used on tight rust and marginally prepared surface. The epoxy finish coat is available in a variety of colors and has good overall chemical resistance. May be used on carbon steel or concrete. Concrete must be clean, rough, and cured at least 28 days. Hand or power tool cleaning, including water blasting, may be used for surface preparation (continued )



501

TABLE 8.4 Continued System E. Aluminum Epoxy Mastic/Acrylic Finish Paint layers One coat aluminum epoxy mastic: 4–6 mils dft (100–150 mm) One coat acrylic finish: 2–3 mils dft (50–75 mm) Properties May be used on tight rust and marginally prepared surfaces. The acrylic finish coat is available in a variety of colors and has good overall chemical resistance. This is an excellent maintenance system. Normally used on carbon steel and concrete System F. Epoxy Mastic/Epoxy Mastic Paint layers One coat epoxy mastic: 4–6 mils dft (100–150 mm) One coat epoxy mastic: 4–6 mils dft (100–150 mm) Properties May be used on tight rust and marginally prepared surfaces. The substrate is protected by the formation of a tight barrier stopping moisture from reaching the surface. Normally used on steel or concrete. Concrete must be clean, rough, and cured at least 28 days. If necessary, hand or power tools may be used for cleaning System G. Epoxy Primer/Epoxy Finish Paint layers One coat epoxy primer: 4–6 mils dft (100–150 mm) One coat epoxy finish: 4–6 mils dft (100–150 mm) Properties An easily applied two coat high build barrier protection is provided with ease of application. Used on carbon steel or concrete Limitations Since these are two component materials, they must be mixed just prior to application. They require additional equipment and more expertise to apply than a single-packed product. Most epoxy finish coats will chalk, fade, and yellow when exposed to sunlight System H. Epoxy Primer Paint layers One coat epoxy primer: 4–6 mils dft (100–150 mm) Properties Normally applied to carbon steel or concrete in protected areas such as the interiors of structures, behind walls and ceilings, or for temporary protection during construction Limitations This is a two component material requiring mixing just prior to application System I. Epoxy Novalac/Epoxy Novalac Paint layers One coat epoxy novalac: 6–8 mils dft (150–200 mm) One coat epoxy novalac: 6–8 mils dft (150–200 mm) Properties An exceptional industrial coating for a wide range of chemical resistance and physical abuse resistance. Has a higher temperature resistance than standard epoxy. May be used to protect insulated piping or for secondary containment. Normally used on carbon steel and concrete surfaces


502


TABLE 8.5 Multilayer Paint Systems Requiring Surface to be Abrasive Blasted in Accordance with SSPC-SP-10 Near White Blast System A. Aluminum–Epoxy Mastic/Aluminum–Epoxy Mastic Paint layers One coat aluminum–epoxy mastic: 4–6 mils dft (100–150 mm) One coat aluminum-epoxy mastic: 4–6 mils dft (100–150 mm) Properties Tolerates poorly prepared surfaces and provides excellent barrier protection. A third coat may be added for additional protection. Can be used on carbon steel and concrete. Concrete must be clean, rough, and cured at least 28 days. If necessary this system can be applied to surfaces that are pitted or cannot be blasted. However, the service life will be reduced. System B. Epoxy Phenolic Primer/Epoxy Phenolic Finish/Epoxy Phenolic Finish Paint layers One coat epoxy phenolic primer: 8 mils dft (200 mm) One coat epoxy phenolic finish: 8 mils dft (200 mm) One coat epoxy phenolic finish: 8 mils dft (200 mm) Properties Because of this system’s outstanding chemical resistance it is often used in areas subject to frequent chemical spills. The finish coats are available in a limited number of colors. Normally used on carbon steel and concrete. Concrete must be clean, rough, and cured at least 28 days. System C. Epoxy Phenolic Primer/Epoxy Phenolic Lining/Epoxy Phenolic Lining Paint layers One coat epoxy phenolic primer: 8 mils dft (200 mm) One coat epoxy phenolic lining: 8 mils dft (200 mm) One coat epoxy phenolic lining: 8 mils dft (200 mm) Properties Because of the system’s outstanding overall chemical resistance it is suitable for lining areas subject to flowing or constant immersion in a variety of chemicals. Normally used on carbon steel and concrete. When used on concrete the surface must be clean, rough, and cured at least 28 days. System D. Epoxy/Epoxy Paint layers One coat epoxy: 4–6 mils dft (100–150 mm) One coat epoxy: 4–6 mils dft (100–150 mm) Properties Two coats of the same product are applied providing a high build protection. Can be used in immersion service without the addition of corrosion inhibitors. When used in potable water systems the product must meet Federal Standard 61. A third coat may be added for additional protection. Normally used on carbon steel and concrete. System E. Coal Tar Epoxy/Coal Tar Epoxy Paint layers One coat coal tar epoxy: 8 mils dft (200 mm) One coat coal tar epoxy: 8 mils dft (200 mm) (continued )



503

TABLE 8.5 Continued Properties Provides excellent barrier protection and is the most economical of the water lining systems or for water immersion. Normally used on carbon steel and concrete. System F. Solventless Elastomeric Polyurethane Paint layers One coat elastomeric polyurethane: 20–250 mils dft (500–6250 mm) Properties Excellent barrier protection. Normally used on carbon steel and concrete. Limitations Must be applied by a knowledgeable contractor.

8.6.3 Area 3. Normally Dry Exteriors This includes such locations as parking lots, water storage tanks, exterior storage sheds, and lighting or power line poles that are exposed to sunlight in a relatively dry location. Under these conditions, oil based paints should last six or more years. These materials that are resistant to ultraviolet rays and are normally rated for exterior use include acrylics, alkyds, silicones, and polyurethanes. Epoxies will lose gloss, normally chalk, and fade rapidly when exposed to UV rays. Recommended systems include A in Table 8.6, C in Table 8.7, A in Table 8.8, and A in Table 8.9. 8.6.4 Area 4. Freshwater Exposure Under this category, the surface to be protected is frequently wetted by freshwater from condensation, splash, or spray. Included are interior or TABLE 8.6 Multilayer Paint Systems Requiring Surface to be Clean, Dry, and Free of Loose Dirt, Oil, and Chemical Contamination System A. Aluminum Epoxy Mastic/Polyurethane Finish Paint layers One coat aluminum epoxy mastic: 4–6 mils dft (100–150 mm) One coat polyurethane finish: 2–4 mils dft (50–100 mm) Properties Excellent over tight rust. Tolerant of minimally prepared steel. May be applied to a wide range of surfaces, but normally used on carbon steel and concrete. This is a premium system to use when cleaning must be minimal. Limitations In order to cure properly, temperature must be above 508F/108C. For lower temperature requirements other aluminum epoxy/urethane mastics may be substituted.


504


TABLE 8.7 Multilayer Paint Systems for New Clean Surfaces, Free of Chemical Contamination System A. Epoxy Mastic Paint layers One coat epoxy mastic: 3–5 mils dft (75–125 mm) Properties Good color selection, excellent chemical resistance, good physical characteristics, ease of maintenance. Used on carbon steel, concrete masonry units, masonry block (a filler is recommended), sheet rock (a sealer is required), wood, polyvinyl chloride, galvanized steel, and other surfaces. Limitations This is a two-component material that is mixed just prior to application. Additional equipment is required and more expertise to apply than a single packaged product. Epoxy solvents may be objectionable to some people. System B. Acrylic Primer/Acrylic Intermediate/Acrylic Finish Paint layers One coat acrylic primer: 2–3 mils dft (50–75 mm) One coat acrylic intermediate: 2–3 mils dft (50–75 mm) One coat acrylic finish: 2–3 mils dft (50–75 mm) Properties This is a single package, water base, low odor, semigloss paint. It possesses excellent weathering and acidic acid resistance. Can be used on most surfaces including carbon steel, concrete, concrete masonry units, masonry block (a block filler is recommended), sheet rock (a sealer is required), wood, polyvinyl chloride, galvanized steel, stainless steel, copper, and fabric. May be applied over existing coatings of any type including inorganic zinc. Limitations Must be protected from freezing during shipping and storage. For application, temperature must be above 608F/168C and will remain so for 2–3 hr after application. System C. Acrylic Primer/Acrylic Finish Paint layers One coat acrylic primer: 2–3 mils dft (50–75 mm) One coat acrylic finish: 2–3 mils dft (50–75 mm) Properties Excellent weathering and acidic chemical resistance, with good color selection. Limitations For best performance metallic surfaces should be abrasive blasted. For mild conditions hand or power cleaning may be sufficient. Paint must be applied when temperature exceeds 608F/168C.

exterior areas that are frequently exposed to cleaning or washing, including steam cleaning. The systems used for these surfaces make use of inorganic zinc as a primer. Inorganic zinc is the best coating that can be applied to steel because it provides the longest term of protection. In some situations, it may be



505

TABLE 8.8 Multilayer Paint Systems Requiring an Abrasive Blast to the Substrate Surface System A. Epoxy Primer/Polyurethane Finish Paint layers One coat epoxy primer: 3–5 mils dft (75–125 mm) One coat polyurethane finish: 2–3 mils dft (50–75 mm) Properties Two coat protection is provided with excellent high gloss finish and long-term color gloss retention. Normally applied to carbon steel and concrete. Limitations Since these are two component materials they must be mixed just prior to application and require additional equipment and more expertise to apply.

necessary to substitute an organic zinc (an organic binder such as epoxy or polyurethane with zinc added) for the inorganic zinc. Recommended systems are B, C, and E of Table 8.4 and A of Table 8.6. 8.6.5 Area 5. Saltwater Exposure This area includes interior or exterior locations on or near a seacoast or industrial environments handling brine or other salts. Under these conditions, the surfaces are frequently wet by salt water and include condensation, splash, or spray. Conditions in this area are essentially the same as for freshwater and the comments for area 4 apply here. Because of the more severe conditions, it is recommended that two coats of the primer be applied for system E of Table 14.1 of Fundamentals of Metallic Corrosion: Atmospheric and Media Corrosion of Metals and system A of Table 8.6. Recommended systems are B, C, and E of Table 8.6 and A of Table 8.6. TABLE 8.9 Multilayer Paint Systems for Previously Painted Surfaces That Have Had Loose Paint and Rust Removed by Hand Cleaning System A. Oleoresin Paint layers One coat oleoresin: 2–4 mils dft (50–100 mm) Properties This very slow drying material penetrates and protects existing surfaces that cannot be cleaned properly with a single coat. Provides long-term protection without peeling, cracking, and other such problems. Easy to apply by spray, brush, roller, or glove. Normally used on carbon steel and weathering galvanized steel. Limitations This material is designed to protect steel that will not see physical abuse. It also stays soft for an extended period of time.


506


8.6.6 Area 6. Freshwater Immersion Wastewaters are also a part of this area. Included are all areas that remain underwater for periods longer than a few hours at a time. Potable and nonpotable water, sanitary sewage, and industrial waste liquids are all included. If the systems recommended are to be used as a tank lining material, it is important that the application be done by experienced workers. In addition, if the coating to be applied is to be in contact with potable water, it is important that the material selected meets the necessary standards and is approved for use by the local health department. Two coats of epoxy (system D in Table 8.5) is frequently used in this service. Recommended systems are F of Table 8.4 and A, D, E, and F of Table 8.5. 8.6.7 Area 7. Saltwater Immersion Areas that remain under water in a coastal environment or industrial area or that are constantly subjected to flowing salt or brine laden water are included in this category. Because of the increased rate of corrosion, a third coat may be added to system F of Table 8.5 and systems A and E of Table 8.5 as additional protection against this more severe corrosion. System D of Table 8.4 and systems A, E, and F of Table 8.5 are recommended for this service. 8.6.8 Area 8. Acidic Chemical Exposure (pH 2.0–5.0) In the chemical process industries, this is one of the most severe environments to be encountered. When repainting, it is important that all surfaces are clean of any chemical residue. Inorganic zinc and zinc filled coatings are not recommended for application in this area. The system selected will be dependent upon the quality of surface preparation, length of chemical exposure, and housekeeping procedures. Decreased cleanup and longer exposure times require a more chemical resistant coating system such as system I in Table 8.4. Other recommendations for this area include systems D, G, and I in Table 8.4 and system B in Table 8.7. 8.6.9 Area 9. Neutral Chemical Exposure (pH 5.0–10.0) This is an area that is not subject to direct chemical attack, but it may be subject to fumes, spillage, or splash. Under these conditions, more protection is required than will be provided by a standard painting system. This would include such locations as clean rooms, packaging areas, hallways, enclosed process areas, instrument rooms, electrical load centers, and other similar locations. A list of potential chemicals that may contact the coating aids in the coating selection. Knowledge of cleanup procedures will also prove helpful.



507

It may be possible to use systems requiring less surface preparation such as system D in Table 8.4, system A in Table 8.6, system A in Table 8.7, and system A in Table 8.8. Recommendations for area 9 are systems A and D in Table 8.4, system A in Table 8.6, systems A and C in Table 8.7, and system A in Table 8.8. 8.6.10 Area 10. Exposure to Mild Solvents This is intended for locations subject to intermittent contact with aliphatic hydrocarbons such as mineral spirits, lower alcohols, glycols, etc. Such contact can be the result of splash, spillage, or fumes. Cross-linked materials, such as epoxies, are best for this service because solvents will dissolve single package coatings. A single coat of inorganic zinc is an excellent choice for immersion service in solvents or for severe splashes and spills. The gloss of a coating system is often reduced as a result of solvent splashes or spills. However, this is a surface effect that usually does not affect the overall protective properties of the coating. Recommended systems for use in this location are A, D, and G of Table 8.4. 8.6.11 Area 11. Extreme pH Exposure This covers locations that are exposed to strong solvents, extreme pHs, oxidizing chemicals, or combinations thereof with high temperatures. The usual choice for coating these areas are epoxy novalacs, epoxy phenolics, and high build polyurethanes. Other special coatings such as the polyesters and vinyl esters may also be considered. However, these systems require special application considerations. Regardless of which coating system is selected, surface preparation is important. An abrasive blast, even on concrete, is required. In addition, all surface contaminants must be removed. When coating concrete, a thicker film is required. System F in Table 8.5 is recommended for optimum protection. Recommended for this location is system I in Table 8.4 and systems B, C, and F in Table 8.5. The foregoing have been generalizations as to what environmental conditions may be encountered, along with suggested coating systems to protect the substrate. Data presented will act as a guide in helping the reader to select the proper coating system. Keep in mind that the surface preparation is critical and should not be skimped on.


9 Cementitious Coatings

Cementitious coatings provide corrosion resistance to substrates such as steel by maintaining the pH at the metal/coating interface above 4, a pH range where steel corrodes at a low rate. The proper selection of materials and their application is necessary if the coating is to be effective. To select the proper material, it is necessary to define the problem: 1. Identify all chemicals that will be present and their concentrations. Knowing pH alone is not sufficient. All pH indicates is whether or not the environment is acid, neutral, or alkaline. It does not identify if the environment is oxidizing, organic or inorganic, alternately acid or alkaline. 2. Is the application fumes, splash, or immersion? 3. What are the minimum and maximum temperatures that the coating will be subjected to? 4. Is the installation indoors or outdoors? Thermal shock and ultraviolet exposure can be deleterious to many resins. 5. How long is the coating expected to last? This can have an effect on the cost. Surface preparation prior to application of the coating is essential. The surface must be free of mill scale, oil, grease, and other chemical contaminants. The surface must be roughened by sandblasting and the coating applied immediately after surface preparation. An intermediate bonding coating is used when adhesion between the substrate and coating is poor or where thermal expansion characteristics are incompatible. Coatings are installed in thicknesses of 1/16 to 1/2 in. (1.5 to 13 mm). They may be applied by casting, troweling, or spraying. The spraying process, known as Gunite or Shotcrete, is particularly useful on systems with unusual geometry or with many sharp bends or corners. It has the advantage that there are no seams that are often weak points as far as corrosion resistance is concerned.

509


510


9.1 Silicates These materials are noted for their resistance to concentrated acids, except hydrofluoric acid and similar fluorinated chemicals at elevated temperatures. They are also resistant to many aliphatic and aromatic solvents. They are not intended for use in alkaline or alternately acid and alkaline environments. This category of coatings includes: 1. Sodium silicate 2. Potassium silicate 3. Silica (silica sol) The alkali silicates form a hard coating by a polymerization reaction, involving repeating units of the structure: OH Si OH

The sodium and potassium silicates are available as two-component systems: filler and binder with the setting agent in the filler. Sodium and potassium silicates are referred to as soluble silicates because of their solubility in water. This prevents their use in many dilute acid services, whereas, they are not affected by strong concentrated acids. This disadvantage becomes an advantage for formulating single component powder systems. All that is required is the addition of water at the time of use. The fillers for these materials are pure silica. The original sodium silicate acid resisting coating uses an inorganic silicate base consisting of two components, a powder and a liquid. The powder is basically quartzite of selected gradation and a setting agent. The liquid is a special sodium silicate solution. When the coating is used, the two components are mixed together, and the hardening occurs by a chemical reaction. This coating may be cast, poured, or applied by guniting. It has excellent acid resistance and is suitable over a pH range of 0.0–7.0. The sodium silicates can be produced over a wide range of compositions of the liquid binder. These properties and the new hardening systems have significantly improved the water resistance of some sodium silicate coatings. These formulations are capable of resisting dilute as well as concentrated acids without compromising physical properties. The potassium silicate materials are less versatile in terms of formulation flexibility than the sodium silicate materials. However, they are less susceptible to crystallization in high concentrations of sulfuric acid so long as metal ion contamination is minimal. Potassium silicate materials are


Cementitious Coatings

511

available with halogen-free hardening systems, thereby, removing remote possibility for catalyst poisoning in certain chemical processes. Chemical setting potassium silicate materials are supplied as two component systems that comprise the silicate solution and the filler powder and setting agent. Setting agents may be inorganic, organic, or a combination of both. The properties of the coating are determined by the setting agent and the alkali–silica ratio of the silicate used. Properties such as absorption, porosity, strength, and water resistance are affected by the choice of the setting agent. Organic setting agents will burn out at low temperatures, thereby, increasing porosity and absorption. Organic setting agents are water soluble and can be leached out if the coating is exposed to steam or moisture. Coatings that use inorganic setting agents are water and moisture resistant. Silicate formulations will fail when exposed to mild alkaline mediums such as bicarbonate of soda. Dilute acid solutions, such as nitric acid, will have a deleterious effect on sodium silicates unless the water resistant type is used. Table 9.1 points out the differences between the various silicate coatings. Silica, or silica sol, types of coatings are the newest of this class of material. They consist of a colloidal silica binding instead of the sodium or potassium silicates with a quartz filler. These materials are two component systems that comprise a powder composed of high quality crushed quartz and a hardening agent that are mixed with colloidal silica that solution to form the coating. TABLE 9.1 Comparative Chemical Resistance: Silicate Coatings Sodium

Potassium

Medium, RT

Normal

Water Resistant

Acetic acid, glacial Chlorine dioxide, water sol. Hydrogen peroxide Nitric acid, 5% Nitric acid, 20% Nitric acid, over 20% Sodium bicarbonate Sodium sulfite Sulfates, aluminum Sulfates, copper Sulfates, iron Sulfates, magnesium Sulfates, nickel Sulfates, zinc Sulfuric acid, to 93% Sulfuric acid, over 93%

G N N C C R N R R G G G G G G G

G N R R R R N R R G G G G G G G

Normal

Halogen Free

R R N R R R N N R R R R R R R R

R R N R R R N N R R R R R R R R

Note: RT, room temperature; R, recommended; N, not recommended; G, potential failure, crystalline growth; C, conditional.


512


These coatings are recommended for use in the presence of hot concentrated sulfuric acid. They are also used for weak acid conditions up to a pH of 7.

9.2 Calcium Aluminate Coatings of this type consist of calcium aluminate-based cement and various inert ingredients and are supplied in powder form to be mixed with water when used. They may be applied by casting, pouring, or guniting. Calcium aluminate-based coatings are hydraulic and consume water in their reaction mechanism to form hydrated phases. This is similar to portland cement compositions; however, their rates of hardening are very rapid. Essentially, full strength is reached within 24 h at 738F (238C). They have better acid resistance than portland cement, but they are not useful in acids below pH 4.5–5. They are not recommended for alkali service above a pH of 10, nor are they recommended for halogen service. Refer to Table 9.2 for the chemical resistance of calcium aluminate and portland cement.

9.3 Portland Cement Portland cement is made from limestone or other natural sources of calcium carbonate, clay (a source of silica), alumina, ferric oxide, and minor impurities. After grinding, the mixture is fired in a kiln at approximately 25008F (11378C). The final product is ground to a fineness of about 10 mm, TABLE 9.2 Chemical Resistance of Calcium Aluminate and Portland Cement Cement Type pH range Water resistance Sulfuric acid Hydrochloric acid Phosphoric acid Nitric acid Organic acids Solvents Ammonium hydroxide Sodium hydroxide Calcium hydroxide Amines

Calcium Aluminate

Portland Cement

4.5–10 E X X P X F G F F F F

7–12 E X X X X F G G F G G

Note: E, excellent; G, good; F, fair; P, poor; X, not recommended.


Cementitious Coatings

513

and it is mixed with gypsum to control setting. When mixed with water, the portland cement forms a hydrated phase, and it hardens. As the cement hardens, a chemical reaction takes place. The two most important reactions are the generation of calcium hydroxide and of tricalcium silicate hydrate. The calcium hydroxide generated could, theoretically, be as high as 20% of the weight of the cement, producing an alkalinity that at the solubility of lime, results in an equilibrium pH of 12.5. Steel that has been coated with cement is passivated as a result of the hardened materials. The alkalinity of the coating is provided by the presence of calcium oxide (lime). Any material that will cause the calcium oxide or hydroxide to be removed, lowering the pH, will prove detrimental and cause solution of the cement hydrates. Contact with organic or inorganic acids can cause this to happen. Organic acids can be generated when organic materials ferment. When carbon dioxide dissolves in water that may be present on the cement, weak carbonic acid is produced. The weak carbonic acid lowers the pH of the cement solution, allowing the coated steel to corrode. This is sometimes referred to as the carbonation of cement. Sulfates will also cause portland cement to deteriorate. In addition to being able to produce sulfuric acid that is highly corrosive to portland cement, sulfates are reactive with some additives used in the formulations. Refer to Table 9.2.


10 Coatings for Concrete

The life of concrete can be prolonged by providing a coating that will be resistant to the pollutants present. These coatings are referred to as monolithic surfacings. Before selecting an appropriate coating, consideration must be given to the condition of the concrete and the environment that the concrete will be exposed to. Proper surface preparation is essential. Surface preparations can be different for freshly placed concrete than for old concrete. When concrete is poured, it is usually held in place by means of steel or wood forms that are removed when the concrete is still in its tender state. To facilitate their removal, release agents are applied to the forms prior to pouring. Oils, greases, and proprietary release agents are left on the surface of the concrete. These must be removed if they will interfere with the adhesion of subsequent coatings. Quite often, curing compounds are applied to fresh concrete as soon as practical after the forms have been removed. These are liquid membranes based on waxes, resins, chlorinated rubber, or other film formers, usually in a solvent. Pretesting is necessary to determine whether or not they will interfere with the coating to be applied. Generally, admixtures that are added to concrete mixes in order to speed up or slow down the cure, add air to the mix, or obtain special effects will not interfere with surface treatments to improve durability. The concrete supplier can furnish specific data regarding the admixtures. If in doubt, try a test patch of the coating material to be used. It is essential that water from subslab ground sources be eliminated or minimized since migration through the concrete may create pressures at the bond line of water resistant barriers. As discussed in Chapter 9 under portland cement coating, when water is added to portland cement, a chemical reaction takes place during the hardening. This reaction produces calcium hydroxide and tricalcium silicate hydrate. The alkalinity of concrete is provided by the presence of calcium oxide from the cement. Consequently, concrete attack can be due to chemicals that react with the portland cement binder and form conditions that physically deteriorate the material. Any material that will

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cause the calcium oxide or hydroxide to be removed, lowering the pH of the cement mix, will cause instability and solution of the cement hydrates. The most common cause for the deterioration of concrete results from contact with inorganic and organic acids. Those that form soluble salts with calcium oxide or calcium hydroxide are the most aggressive. Typical compounds that can cause problems include sour milk, industrial wastes, fruit juices, sonic ultrapure waters, and organic materials that ferment and produce organic acids. Typical chemical families found in various types of chemical processing industry plants and their effect on concrete are shown in Table 10.1.

10.1 Surface Preparation It is essential that the concrete surface be property prepared prior to application of the coating. The surfaces of cement containing materials may contain defects that require repair before the application of the coating. In general, the surface must be thoroughly cleaned and all cracks repaired. Unlike specifications for the preparation of steel prior to coating, there are no detailed standard specifications for the preparation of concrete surfaces. In most instances, it is necessary to follow the instructions supplied by the coating manufacturer. Specifications can range from the simple surface cleaning that provides a clean surface without removing concrete from the substrate, to surface abrading that provides a clean roughened surface, to acid etching that also provides a clean roughened surface. 10.1.1 Surface Cleaning Surface cleaning is accomplished by one of the following means: 1. Broom sweeping 2. Vacuum cleaning 3. Air blast 4. Water cleaning 5. Detergent cleaning 6. Steam cleaning Water cleaning and detergent cleaning will not remove deep embedded soils in the pores of the concrete surfaces. In addition, these methods saturate the concrete that then requires a drying period (not always practical).


Coatings for Concrete

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TABLE 10.1 Effects of Various Chemicals on Concrete Chemical Chemical Plants Acid waters pH 6.5 or less Ammonium nitrate Benzene Sodium hypochlorite Ethylene Phosphoric acid Sodium hydroxide, 20% and above Food and beverage plants Almond oil Beef fat Beer Buttermilk Carbonic acid (soda water) Cider Coconut oil Corn syrup Fish oil Fruit juices Lard or lard oil Milk Molasses Peanut oil Poppyseed oil Soybean oil Sugar Electric generating utilities Ammonium salts Coal Hydrogen sulfide Sulfuric acid (10–80%) Sulfur dioxide Pulp and paper mills Chlorine gas Sodium hypochlorite Sodium hydroxide Sodium sulfide Sodium sulfate Tanning liquor

Effect on Concrete Disintegrates slowly Disintegrates Liquid loss by penetration Disintegrates slowly Disintegrates slowly Disintegrates slowly Disintegrates slowly Disintegrates slowly Solid fat disintegrates slowly, malted fat more readily May contain, as fermentation products, acetic, carbonic, lactic, or tannic acids which disintegrate slowly Disintegrates slowly Disintegrates slowly Disintegrates slowly Disintegrates slowly Disintegrates slowly Disintegrates slowly Disintegrates Lard disintegrates slowly, lard oil more quickly No effect Disintegrates slowly above 1208F/498C Disintegrates slowly Disintegrates slowly Disintegrates slowly Disintegrates slowly Disintegrates Sulfides leaching from damp coal may oxidize to sulfurous or sulfuric acid, disintegrates Dry, no effect; in moist oxidizing environments converts to sulfurous acid and disintegrates slowly Disintegrates rapidly With moisture forms sulfurous acid which disintegrates rapidly Slowly disintegrates moist concrete Disintegrates slowly Disintegrates concrete Disintegrates slowly Disintegrates concrete of inadequate sulfate resistance Disintegrates if acid


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10.1.2 Surface Abrading Surface abrading can be accomplished by 1. Mechanical abrading 2. Water blasting 3. Abrasive blasting Of the three methods to produce a roughened surface, the most technically effective is abrasive blasting by means of sandblasting or shot blasting followed by broom sweeping, vacuum cleaning, or an air blast to remove the abrasive. However, in some instances this may not be a practical approach. 10.1.3 Acid Etching Acid etching is a popular procedure used for both new and aged concrete. It must be remembered that during this process, acid fumes will be evolved that may be objectionable. Also thorough rinsing is required that saturates the concrete. This may necessitate a long drying period, depending on the coating to be used.

10.2 Coating Selection The coating to be selected will depend on the physical properties and conditions of the concrete as well as the environmental conditions. Factors such as alkalinity, porosity, water adsorption and permeability, and weak tensile strength must be considered. The tendency of concrete to crack, particularly on floors, must also enter into the decision. Floor cracks may develop as a result of periodic overloading or from drying shrinkage. Drying shrinkage is not considered a working movement, whereas, periodic overloading is. In the former, a rigid flooring system could be used, whereas, in the latter, an elastomeric caulking of the moving cracks would be considered. Selection may be influenced by the presence of substrate water during coating. If the concrete cannot be dried, one of the varieties of water based or water tolerant systems should he considered. When aggressive environments are present, the surface profile and surface porosity of the concrete must be taken into account. If complete coverage of the substrate is required, specification of film thickness or number of coats may need to be modified. Block fillers may be required. In a nonaggressive atmosphere, an acrylic latex coating may suffice. Specific environmental conditions will dictate the type of coating required. Not only do normal atmospheric pollutants have to be considered, but any specific local pollutants will also have to be taken into account.



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Also to be considered are the local weather conditions that will result in minimum and maximum temperatures as seasons change. Also to be considered are the possibilities of spillage of chemicals on the surface. Coatings can be applied in various thicknesses depending upon the environment and contaminants. Thin film coatings are applied at less than 20 mils dry film thickness. Commonly used are epoxies that may be formulations of polyamides, polyamines, polyesters, or phenolics. These coatings will protect against spills of hydrocarbon fuels, some weak solutions of acids and alkalies, and many agricultural chemicals. Epoxies can also be formulated to resist spills of aromatic solvents such as xylol or toluol. Most epoxies will lose some of their gloss and develop a “chalk face” when exposed to weather. However, this does not affect their chemical resistance. Medium film coatings are applied at approximately 20–40 mils dry film thickness. Epoxies used in this category are often flake filled to give them rigidity, impact strength, and increased chemical resistance. The flakes can be mica, glass, or other inorganic platelets. Vinyl esters are also used in this medium film category. These coatings exhibit excellent resistance to many acids, alkalies, hypochlorites, and solvents. Vinyl esters may also be flake filled to improve their resistance. Sonic vinyl esters require the application of a low viscosity penetrating primer to properly cleaned and profiled concrete before application, whereas, others may he applied directly. Thick film coatings are installed by two means. The specialty epoxy types are mixed with inorganic aggregates and trowel applied. The polyesters and vinyl esters are applied with a reinforcing fiberglass mat. Table 10.2 provides a guideline for specifying film thickness. The most popular monolithic surfacings are formulated from the following resins: 1. Epoxy, including epoxy novolac 2. Polyester 3. Vinyl ester, including vinyl ester novolac 4. Acrylic 5. Urethane 6. Phenolic novolacs

10.3 Installation of Coatings As with the application of any coating system, proper surface preparation and installation techniques are essential. Basic preparations for the application of a coating are as follows:


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TABLE 10.2 Guidelines for Specifying Film Thickness Film Thickness Contaminant Aliphatic hydrocarbons Aromatic hydrocarbons Organic acids Weak Moderate Strong Inorganic acids Weak Moderate Strong Alkalies Weak Moderate Strong Bleach liquors Oxygenated fuels Fuel additives Deionized water Methyl ethyl ketone Fermented beverages Seawater Hydraulic/brake fluids

Thin

Medium

Thick

X X

X X

X

X X

X

X

X X X X X X X X

X

X X X X X X

X

X X X

X

X

1. Substrate must be free of cracks and be properly sloped to drains. 2. New, as well as existing slabs, should have a coarse surface profile, be clean and dry, and be free of contaminants. 3. In general, slab and materials to be installed should have a temperature of 65–858F/18–298C. If necessary, special catalysts and hardening systems are available to accommodate higher or lower temperatures. 4. Manufacturers’ directions should be adhered to regarding the priming of the substrate prior to applying the monolithic surfacing. 5. Individual and combined components should be mixed thoroughly at a maximum speed of 500 rpm to minimize air entrapment. 6. Prior to curing, the surface must be protected from moisture and contamination. Monolithic surfacings may be installed by a variety of methods, many that are the same methods used in the portland cement concrete industry.



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The primary methods are: 1. Hand troweled 2. Power troweled 3. Spray 4. Pour in place/self-level 5. Broadcast Small areas, or areas with multiple obstructions, should be hand troweled. Topcoat sealers should be applied to provide imperviousness and increased density with a smooth, easy-to-clean finish. Large areas with a minimum of obstructions are best handled with power troweling. The minimum thickness would be 1/4 in. (6.5 mm). The density of the finish can be improved by the use of appropriate sealers. For areas subjected to aggressive corrosion, spray application is recommended. The consistency of the material can be formulated to control slump and type of finish. This permits the material to be sprayed on vertical and overhead surfaces including structural components with thicknesses of 1/16 to 3/32 in. (1.5 to 2.4 mm) as is suitable for light duty areas. Economical and aesthetically attractive floors can be applied by the broadcast system where resins are “squeegee” applied to the concrete stab. Filler or colored quartz aggregates of varying color and size are sprinkled or broadcast into the resin. Excess filler and quartz are vacuumed or swept from the floor after the resin has set. This results in a floor thickness of 3/32 to 1/8 in. (2 to 3 mm). This type of floor is outstanding for light industrial and interior floors.

10.4 Epoxy and Epoxy Novolac Coatings The three most often used epoxy resins for monolithic surfacings are the bisphenol A, bisphenol F (epoxy novolac), and epoxy phenol novolac. These base components are reacted with epichlorhydrin to form resins of varying viscosity and molecular weight. The hardening system employed to effect the cure or solidification will determine the following properties of the cured system: 1. Chemical and thermal resistance 2. Physical properties 3. Moisture tolerance 4. Workability 5. Safety during use


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Bisphenol A epoxy is the most popular, followed by the bisphenol F that is sometimes referred to as an epoxy novolac. The epoxy phenol novolac is a higher viscosity resin that requires various types of diluents or resin blends for formulating coatings. The bisphenol A resin uses the following types of hardeners: 1. Aliphatic amines 2. Modified aliphatic amines 3. Aromatic amines 4. Others Table 10.3 shows effects of the hardener on the chemical resistance of the finished coating of bisphenol A systems for typical compounds. Table 10.4 provides a comparison of the general chemical resistance of optimum chemical resistant bisphenol A, aromatic amine cured, with bisphenol F resin systems. Amine hardening systems are the most popular for ambient temperature curing epoxy coatings. These systems are hygroscopic and can cause allergenic responses to sensitive skin. These responses can be minimized or virtually eliminated by attention to personal hygiene and the use of protective creams on exposed areas of skin, i.e., face, neck, arms, and hands. Protective garments, including gloves, are recommended when using epoxy materials. Epoxies are economical, available in a wide range of formulations and properties, and offered from many manufacturers. Formulations are available for interior as well as exterior applications. However, when installed outside, moisture from beneath the slab can affect adhesion and cause blistering. The typical epoxy system is installed in layers of primer, base, and finish coats. Overall, the installation can take several days. Epoxies should not be TABLE 10.3 Types of Epoxy Hardeners and Their Effect on Chemical Resistance Hardeners Medium

Aliphatic Amines


Aromatic Amines

Acetic acid, 5–10% Benzene Chromic acid, !5% Sulfuric acid, 25% Sulfuric acid, 50% Sulfuric acid, 75%

C N C R C N

N N N C N N

R R R R R R

R, recommended; N, not recommended; C, conditional. Source: From A.A. Boova. 1996. Chemical resistant mortors, grouts and monolithic surfacings, in Corrosion Engineering Handbook, P.A. Schweitzer, Ed., New York: Marcel Dekker, pp. 459–487.



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TABLE 10.4 Comparative Chemical and Thermal Resistance of Bisphenol A, Aromatic AmineCured vs. Bisphenol F (Epoxy Novolac) Medium, RT Acetone Butyl acetate Butyl alcohol Chromic acid, 10% Formaldehyde, 35% Gasoline Hydrochloric acid, to 36% Nitric acid, 30% Phosphoric acid, 50% Sulfuric acid, to 50% Trichloroethylene Maximum temperature, 8F/8C

Bisphenol A

Bisphenol F

N C C C E E E N E E N 160/71

N E E E G E E C E E G 160/71

RT, room temperature; C, conditional; N, not recommended; E. excellent; G, good. Source: From A.A. Boova. 1996. Chemical resistant mortars, grouts and monolithic surfacings, in Corrosion Engineering Handbook, P.A. Schweitzer, Ed., New York: Marcel Dekker, pp. 459–487.

applied to new concrete before it has reached full strength (approximately twenty eight days). Table 10.5 provides the atmospheric corrosion resistance of monolithic floor surfacings.

TABLE 10.5 Atmospheric Corrosion Resistance of Monolithic Concrete Surfacings Atmospheric Pollutant Surfacing Epoxy–bisphenol A Aromatic amine hardener Epoxy novolac Polyesters Isophthalic Chlorendic Bisphenol A fumarate Vinyl esters Acrylics Urethanes

NOx

H2S

SO2

CO2

UV

Chloride Salt

R

X

X

R

R

R

R

R

R

X

X

R

R

R

R

R

R R R

R R R

X X X

R R R

RS RS RS

R R R

R R R

R R R

R R R

R

R R X

R R

R R R

R R R

R R

R R

Weather Ozone

R, resistant; X, not resistant; RS, resistant when stabilized. Source: From P.A. Schweitzer. 1999. Atmospheric Degradation and Corrosion Control, New York: Marcel Dekker.


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TABLE 10.6 Corrosion Resistance of Bisphenol A and Bisphenol F Epoxies Hardeners Aromatic Amines Corrodent, RT Acetic acid, 5–10% Acetone Benzene Butyl acetate Butyl alcohol Chromic acid, 5% Chromic acid, 10% Formaldehyde, 35% Gasoline Hydrochloric acid, to 36% Nitric acid, 30% Phosphoric acid, 50% Sulfuric acid, 25% Sulfuric acid, 50 Sulfuric acid, 75% Trichloroethylene

Bisphenol

Aliphatic Amines


A

F

C U U U R U U R R U U U R U U U

U U U U R U U R R U U U U U U U

R U R U R R U R R R U R R R U U

U R R R R R R R R U R R R U R

RT, room temperature; R, recommended; U, unsatisfactory. Source: From P.A. Schweitzer. 1998. Encyclopedia of Corrosion Technology, New York: Marcel Dekker.

The bisphenol Fs (epoxy novolacs) are essentially premium grade epoxy resins providing an increased chemical resistance. They are also available in a wide range of formulations and from many manufacturers. The primary advantages in the use of epoxy novolacs is in their improved resistance to higher concentrations of oxidizing and nonoxidizing acids, and aliphatic and aromatic solvents. Refer to Table 10.6. The novolacs arc more expensive than the bisphenol A epoxies and can discolor from contact with sulfuric and nitric acids. For exposure to normal atmospheric pollutants, bisphenol A epoxies are satisfactory. However, if the surface is to be exposed to other more aggressive containments, then the novolacs should be considered. Table 10.7 provides a comparison of the chemical resistance of various monolithic surfacings.

10.5 Polyester Coatings Polyester coatings were originally developed to resist chlorine dioxide. The three types of unsaturated polyesters most commonly used are



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TABLE 10.7 Comparative Chemical Resistance 1 Medium, RT Acetic acid, to 10% Acetic acid, 10–15% Benzene Butyl alcohol Chlorine, wet, dry Ethyl alcohol Fatty acids Formaldehyde, to 37% Hydrochloric acid, to 36% Kerosene Methyl ethyl ketone, 100% Nitric acid, to 20% Nitric acid, 20–40% Phosphoric acid Sodium hydroxide, to 25% Sodium hydroxide, 25–50% Sodium hypochlorite, to 6% Sulfuric acid, to 50% Sulfuric acid, 50–75% Xylene

2

3

A

B

C

D

E

F

G

R C C R C R C R C R N N N R R R C R C N

R R R C C C R R R R N N N R R C R R R R

R C R R C R C R R R N R R R R R R R R R

R R R R R R R R R R N R R R N N R R R R

R R N R R R R R R R N R N R R R R R C R

R C R N R R R R R R N R N R R C R R R N

R R R R R R R R R R N R C R R R R R R R

RT, room temperature; 1-A, bisphenol A epoxy—aliphatic amine hardener; 1-B, bisphenol A epoxy—aromatic amine hardener; 1-C, bisphenol F epoxy (epoxy novolac); 2-D, polyester resin—chlorendic acid type; 2-E, polyester resin—bisphenol A fumarate type; 3-F, vinyl ester resin; 3-G, vinyl ester novolac resin; R, recommended; N, not recommended; C; conditional. Source: From A.A. Boova. 1996. Chemical resistant mortars, grouts and monolithic surfacings, in Corrosion Engineering Handbook, P.A. Schweitzer, Ed., New York: Marcel Dekker, pp. 459–487.

1. Isophthalic 2. Chlorendic acid 3. Bisplienol A fumarate The chlorendic and bisphenol A resins offer improved chemical resistance, higher thermal capabilities, and improved ductility with less shrinkage. The bisphenol A resins provide improved resistance to alkalies and essentially equivalent resistance to oxidizing mediums. Refer to Table 10.5 for the resistance of the polyester resins to atmospheric containments and to Table 10.8 for the comparative chemical resistance of the various polyester resins. Polyester resins are easily pigmented for aesthetic considerations. The essentially neutral curing systems provide compatibility for application to many substrates including concrete. Properly formulated polyester resins


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TABLE 10.8 Comparative Chemical Resistance of Various Polyester Resins Medium, RT Acids, oxidizing Acids, nonoxidizing Alkalies Salts Bleaches Maximum temperature, 8F/8C

Isophthalic

Chlorendic


R R N R R 225/107

R R N R R 260/127

R R R R R 250/121

RT, room temperature; R, recommended; N, not recommended. Source: From A.A. Boova. 1996. Chemical resistant mortars, grouts and monolithic surfacings, in Corrosion Engineering Handbook, P.A. Schweitzer, Ed., New York: Marcel Dekker, pp. 459–487.

provide installation flexibility to a wide range of temperatures, humidities, and containments; encountered on most construction sites. Polyester formulations have limitations such as 1. Strong aromatic odor that can be offensive for certain indoor and confined space applications 2. Shelf life limitations that can be controlled by low temperature storage (below 608F/158C) of the resin component. Table 10.9 provides the chemical resistance of chlorendic and bisphenol A fumarate rosins in the presence of selected corrodents. 10.5.1 Vinyl Ester/Vinyl Ester Novolac Coatings Vinyl ester resins are addition reactions of methacrylic acid and epoxy resin. These resins have many of the same properties as the epoxy, acrylic, and bisphenol A fumarate resins. The vinyl ester resins are the most corrosion resistant of any of the monolithic surfacing systems, and they are also the most expensive and difficult to install. They are used when extremely corrosive conditions are present. The finished flooring is vulnerable to hydrostatic pressure and vapor moisture transmission. Refer to Table 10.5 for their resistance to atmospheric corrosion and Table 10.10 for their resistance to selected corrodents. The major advantage of these resins are their resistance to most oxidizing mediums and high concentrations of sulfuric acid, sodium hydroxide, and many solvents.



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TABLE 10.9 Chemical Resistance of Chlorendic and Bisphenol A Fumarate Resins Polyester Corrodent, RT Acetic acid, glacial Benzene Chlorine dioxide Ethyl alcohol Hydrochloric acid, 36% Hydrogen peroxide Methanol Methyl ethyl ketone Motor oil and gasoline Nitric acid, 40% Phenol, 5% Sodium hydroxide, 50% Sulfuric acid, 75% Toluene Triethanolamine Vinyl toluene

Chlorendic


U U R R R R R U R R R U R U U U

U U R R R U R U R U R R U U R U

RT, room temperature; R, recommended; U, unsatisfactory. Source: From P.A. Schweitzer. 1998. Encyclopedia of Corrosion Technology, New York: Marcel Dekker.

Vinyl ester resins also have the disadvantages of having 1. Strong aromatic odor for indoor or confined space applications 2. Shelf life limitation of the resins require refrigerated storage below 608F/158C to extend its useful life.

10.6 Acrylic Coating Acrylic monolithic coatings are suitable for interior or exterior applications with relatively benign atmospheric exposures. Refer to Table 18.5 of Fundamentals of Metallic Corrosion: Atmospheric and Media Corrosion of Metals. They excel at water and weather resistance, and are best at “breathing” in the presence of a moisture transmissive problem in the stab. They are intended for protection against moderate corrosion environments. The advantages for their use are as follows: 1. They are the easiest of the resin systems to mix and apply by using pour-in-place and self-leveling techniques. 2. Because of their outstanding weather resistance, they are equally appropriate for indoor or outdoor applications.


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Corrosion of Linings and Coatings TABLE 10.10 Resistance of Vinyl Ester and Vinyl Ester Novolac to Selected Corrodents Vinyl Ester Corrodent Acetic acid, glacial Benzene Chlorine dioxide Ethyl alcohol Hydrochloric acid, 36% Hydrogen peroxide Methanol Methyl ethyl ketone Motor oil and gasoline Nitric acid, 40% Phenol, 5% Sodium hydroxide, 50% Sulfuric acid, 75% Toluene Triethanolamine Vinyl toluene Maximum temperature, 8F/8C

Vinyl Ester

Novolac

U R R R R R U U R U R R R U R U 220/104

R R R R R R R U R R R R R R R R 230/110

R, recommended; U, unsatisfactory. Source: From P.A. Schweitzer. 1998. Encyclopedia of Corrosion Technology, New York: Marcel Dekker.

3. They are the only system that can be installed at below freezing temperatures (258F/K48C) without having to use special hardening or catalyst systems. 4. They are the fastest set and cure of all the resins. 5. They are the easiest to pigment and, with the addition of various types of aggregate, can be aesthetically attractive. 6. They are equally appropriate for maintenance and new construction, and they bond well to concrete. The disadvantage of the acrylic coating system is the aromatic odor in indoor or confined spaces.

10.7 Urethane Coatings Monolithic urethane flooring systems offer the following advantages: 1. They are easy to mix and apply using the pour-in-place, selflevel technique.



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2. Systems are available for indoor or outdoor installations. 3. The elastomeric quality of the systems provides underfoot comfort. 4. They have excellent sound-deadening properties. 5. They have excellent resistance to impact and abrasion. 6. They are excellent waterproof flooring systems for above-grade light and heavy duty floors. 7. They are capable of bridging Cracks in concrete 1/16 in. (1.5 mm) wide. As with the acrylics, the urethanes are intended for protection against moderate to light corrosion environments. Standard systems are effective at temperatures of 10 to 1408F(K24 to 608C). High temperature systems are available with a range of 10 to 1808F(K24 to 828C). Refer to Table 10.11 for the comparative chemical resistance of urethane and acrylic systems. The acrylic and urethane systems have substantially different physical properties. The acrylic flooring systems are extremely hard and are too brittle for applications subjected to excessive physical abuse such as impact, whereas, the inherent flexibility and impact resistance of the urethanes offer potential for this type of application. Table 10.12 provides

TABLE 10.11 Comparative Chemical Resistance: Urethane vs. Acrylic Systems Urethane Medium, RT Acetic acid, 10% Animal oils Boric acid Butter Chromic acid, 5–10% Ethyl alcohol Fatty acids Gasoline Hydrochloric acid, 20–36% Lactic acid, above, 10% Methyl ethyl ketone, 100% Nitric acid, 5–10% Sulfuric acid, 20–50% Water, fresh Wine

Acrylic

Standard

High Temperature

G G E G C N F E F F N G G E G

G G E F C N F N C C N C C E G

C N E N C N N N C C N F C E F

RT, room temperature; E, excellent; G, good; F, fair; C, conditional; N, not recommended. Source: From A.A. Boova. 1996. Chemical resistant mortars, grouts and monolithic surfacings, in Corrosion Engineering Handbook, P.A. Schweitzer, Ed., New York: Marcel Dekker, pp. 459–487.


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TABLE 10.12 Minimum Physical and Thermal Properties of Acrylic Monolithic Surfacing and Urethane Monolithic Surfacings Acrylics

Urethanes

Property

Monolithic

Standard

High Temperature

Tensile, psi (MPa) ASTM test method C-307 Flexural, psi (MPa) ASTM test method C-580 Compressive, psi (MPa) ASTM test method C-579 Bond to concrete Maximum temperature, 8F/8C

1000 (7)

650 (5)

550 (5)

2500 (17)

1100 (8)

860 (6)

8000 (55)

2500 (17)

1500 (10)

Concrete fails 150/66



Source: From A.A. Boova. 1996. Chemical resistant mortars, grouts and monolithic surfacings, in Corrosion Engineering Handbook, P.A. Schweitzer, Ed., New York: Marcel Dekker, pp. 459–487.

physical and thermal properties for the acrylic and urethane flooring systems.

10.8 Phenolic/Epoxy Novolac Coatings In order to satisfy the need to provide a coating system that has ability to bridge cracks and provide improved corrosion resistance, medium build coating systems have been developed. The phenolic/epoxy novolac system is capable of bridging cracks and providing outstanding corrosion resistance. One such system uses a low viscosity penetrating epoxy primer. Low viscosity allow the primer to be used for areas that need a fast turnaround by quickly “wetting out” the substrate. If surface deterioration or preparation presents an unacceptably rough surface, the surface can be smoothed further by using a pigmented, high solid/high build epoxy polyamide filler/sealer. For deep pits, the crack filler used is a two component epoxy paste developed specifically for sealing and smoothing out applications on concrete. The crack filler can be used to fill and smooth hairline cracks, bug holes, gouges, or divots when minimal movement of the substrate is expected.



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TABLE 10.13 Compatibility of Phenolic with Selected Corrodents Maximum Temperature Chemical Acetic acid, 10% Acetic acid, glacial Acetic anhydride Acetone Aluminum sulfate Ammonium carbonate Ammonium chloride, to sat. Ammonium hydroxide, 25% Ammonium nitrate Ammonium sulfate Aniline Benzene Butyl acetate Calcium chloride Calcium hypochlorite Carbonic acid Chromic acid Citric acid, conc. Copper sulfate Hydrobromic acid, to 50% Hydrochloric acid, to 38% Hydrofluoric acid Lactic acid, 25% Methyl isobutyl ketone Muriatic acid Nitric acid Phenol Phosphoric acid, 50–80% Sodium chloride Sodium hydroxide Sodium hypochlorite Sulfuric acid, 10% Sulfuric acid, 50% Sulfuric acid, 70% Sulfuric acid, 90% Sulfuric acid, 98% Sulfurous acid

8F

8C

212 70 70 X 300 90 80 X 160 300 X 160 X 300 X 200 X 160 300 200 300 X 160 160 300 X X 212 300 X X 250 250 200 70 X 80

100 21 21 X 149 32 27 X 71 149 X 71 X 149 X 93 X 71 149 93 149 X 71 71 149 X X 100 149 X X 121 121 93 21 X 27

The chemicals listed are in the pure state or in a saturated solution unless otherwise indicated. Compatibility is shown to the maximum allowable temperature that data is available for. Incompatibility is shown by an X.

To provide maximum corrosion resistance a two component phenolic/ epoxy novolac coating can be used. The phenolic coating provides resistance to high concentrations of acids, particularly to sulfuric acid at elevated temperatures, Refer to Table 10.13 for the compatibility of phenolic with selected corrodents.


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References 1. 2. 3.

P.A. Schweitzer. 1999. Atmospheric Degradation and Corrosion Control, New York: Marcel Dekker. A.A. Boova. 1996. Chemical resistant mortars, grouts and monolithic surfacings, in Corrosion Engineering Handbook, P.A. Schweitzer, Ed., New York: Marcel Dekker, pp. 459–487. P.A. Schweitzer. 1998. Encyclopedia of Corrosion Technology, New York: Marcel Dekker.


11 Corrosion Monitoring

It is essential for operators of industrial process plants to have a program for controlling corrosion. For such a program to be effective, it should facilitate safe operation of the process unit over its intended life and maximize the economic return to the owner. To accomplish these objectives, a corrosion control program should consider: characteristics (toxicity, flammability, etc.) of the process; selection of construction materials; control of operating conditions; addition of neutralizing or inhibition chemicals; and monitoring to ensure that anticipated results are obtained. Selection of construction materials almost always involves a compromise between expensive and often hard-to-obtain alloys highly resistant to corrosion by the process under any conceivable operating conditions and less expensive, more available materials that are more susceptible to corrosion. Often, a material can have acceptable resistance to a process at design conditions but corrode at very high rates during process upsets. Particularly in these cases, on-line monitoring and control of process operating parameters and direct on-line monitoring of corrosion rates are essential to an effective program. Several types of materials are often used in conjunction in the construction of process facilities. For instance, corrosionresistant alloys are used in particularly susceptible equipment (heat exchanger tubes, for example) with less expensive materials used elsewhere in the process. It is, of course, essential that the behavior of various metals in the anticipated operating environment be known in advance of selection. whereas there is a vast array of available literature on the subject, laboratory and field trials are often performed to verify theoretical predictions or tryout new materials before a commitment is made to use them in the process unit. Sometimes a less expensive material, that would otherwise be unacceptable because of low corrosion resistance can still be the best choice when used in conjunction with a chemical corrosion inhibitor injection system or an anodic or cathodic protection system. There are many operating and environmental parameters that can affect the corrosion of a metal—changes in any that can greatly accelerate the corrosion rate. Without early detection and accurate measurement of the impact of these changes, costly and potentially hazardous damage can occur 533


534


before corrections are made. Accurate and timely corrosion measurement is, therefore, an essential part of almost all corrosion control programs. The technology of corrosion detection and measurement has rapidly advanced in the recent past, so today’s corrosion engineer has many proven techniques available for both laboratory analysis and on-line monitoring to devise and manage an effective corrosion control program for his (her) particular plant process and environmental conditions.

11.1 Measuring and Monitoring Corrosion As used herein, measurement of corrosion refers to any technique that can be used to determine the effects of corrosion: 1. While the facilities are in operation 2. During shutdowns 3. While the laboratory analyses are performed outside the process equipment Monitoring refers to a special group of measurement techniques that are suitable for use while the facility is in operation. A comprehensive corrosion control program should include several techniques because no single technique is capable of providing all the information necessary in a timely manner. An overview of measurement techniques is presented below with emphasis on those useful in practical on-line monitoring. 11.1.1 Radiography Radiography (x-ray) permits two-dimensional views of the piping or equipment walls and is suitable for detecting major flaws or a severe corrosive attack when results are compared to an earlier (or baseline) study. Radiography is not suitable for detecting small changes in residual wall thickness because of accuracy limitations. Radiography is a measurement technique that requires specialized equipment and trained operators, usually provided by contractor personnel, and is not currently used in continuous on-line monitoring. 11.1.2 Ultrasonic Measurement Ultrasonic measurement techniques are similar to radiography in that specialized equipment is required, and they are almost exclusively used for measurement rather than monitoring. There are several types of ultrasonic equipment. A scan provides a simple depth measurement from the exterior


Corrosion Monitoring

535

surface of a pipe or vessel to the next interface that reflects sound waves. Generally, this measures wall thickness, but A scan can be occasionally fooled, by midwall pipe flaws. B scan instruments are much more powerful because they produce cross-sectional images similar to x-rays. The C-scan systems produce a three-dimensional view of a surface using complex and expensive equipment. C-scan systems can be very useful for large, critical surfaces such as aircraft skins, but they are much less commonly used in process plants at this time because of cost, speed of coverage, and very large quantity of data produced. 11.1.3 Visual Inspection Visual inspection is rarely practical in a working process plant. However, whenever an opportunity presents itself, full advantage should be taken of it. Only through direct visual inspection can one be absolutely certain as to the condition of a process unit. Consequently, during any turnaround activities, internal visual inspection should be carried out to verify the results of on-line monitoring programs, choose new locations for monitoring, etc. 11.1.4 Destructive Analysis Destructive analysis is less practical than visual inspection but can be important and should, therefore, be performed as often as possible. The most common opportunity arises when piping is replaced for one reason or another. Sections of the replaced piping can then be examined for evidence of stress corrosion cracking (SCC), hydrogen-induced corrosion (HIC), pitting, and any other unusual or unexpected corrosive activity. 11.1.5 Chemical Analysis Chemical analysis is the monitoring of the chemical composition or other chemical characteristics of the process fluids. Because corrosion is an electrochemical phenomenon, chemical analysis can be a useful indicator of corrosivity of the process. In water systems, for instance, pH and conductivity are two parameters frequently monitored to give an indication of corrosivity. Increases in concentrations of corrodents such as H2S or CO2 can also be useful in determining corrosivity, but such measurements require more complex equipment and are usually infrequently made. Another technique that can be useful involves analyzing process streams for the presence of corrosion products, e.g., the quantity of metal and metallic compounds. This type of analysis can yield a good estimate of the current metal loss from corrosion. When compared with previous data, it can be used to establish trends and approximate corrosion rates. Such data must be used with caution, however. For instance, “iron counts” in fluid produced by oil wells can be a good indicator of the amount of corrosion taking place on the casing, tubing, and completion equipment. If iron is present naturally in the


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producing formation, however, information gained from such chemical analysis will most likely be meaningless. 11.1.6 Coupons Coupons are the oldest and simplest device used in the monitoring of corrosion. Coupons are small pieces of metal, usually of a rectangular shape that are inserted in the process stream and removed after a period of time for study. The most common and basic use of coupons is to determine average corrosion rate over the period of exposure. This is accomplished by weighing the coupon before and after exposure (coupons must first be cleaned following exposure to remove corrosion products and any other deposits) and determining the weight loss. The average corrosion rate can easily be calculated from the weight loss, the initial surface area of the coupon, and the time exposed. It is advisable to leave a coupon exposed for at least 30 days to obtain valid corrosion rate information. There are two reasons for this recommended practice. First, a clean coupon generally corrodes much faster than one that has reached equilibrium with its environment. This will cause a higher corrosion rate to be reported in a short test than is actually being experienced on the pipe or vessel. Second, there is an unavoidable potential for error as a result of the cleaning operation. Coupon cleaning procedures are designed to remove all of the deposits without disturbing the remaining uncorroded metal of the coupon. A small amount of the underlying metal is often removed with the deposits, however, and if the actual metal loss from corrosion is small (as would be the case in a short test), the effect of metal removed during cleaning would create a significant error. Care must be taken to correct for this effect. It should be recognized that a coupon can only provide corrosion rate data based on the total weight loss divided by the total time of exposure. A major shortcoming of coupon monitoring is that high corrosion rates for short periods of time may be undetectable and cannot be correlated to process upset conditions. If more frequent information on weight loss is desired, the use of electrical resistance monitoring systems is recommended. In many cases, it is also recommended that coupons and electrical resistance (ER) probes be used in conjunction. One of the most important roles of coupons is to provide information about the type of corrosion present. Unlike ER probes that only detect the amount of metal removed, coupons can be examined for evidence of pitting and other localized forms of attack. It is also important to remember that coupons or monitoring probes indicate the attack of the environment only at the point of exposure. It is important, therefore, that the coupon or probe be installed at representative locations as close as possible to critical points where corrosion measurements are desired (e.g., vessel or pipe walls, tube sheets, trays, lateral lines upstream to major tie-ins). Conditions of flow, temperature, concentration, etc., may change considerably only a few inches away from any given location with resulting differences in corrosion rates. Coupons suspended in the center of a pipeline or vessel may corrode at different rates than coupons



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suspended near the wall of the vessel or pipe, for example. Since corrosive conditions can significantly change from one location to another, coupon data is best used for relative comparisons (changes in the rate or characteristics of corrosion over time at a single point) and to obtain an approximate corrosion rate at a particular point in the system rather than to precisely calculate the corrosion rate. There are several other types of coupons available for specialized analysis. These include disk coupons that can be mounted flush to the pipe wall; ladder coupon holders for mounting coupons at several depths at the same point in the piping; prestressed coupons that are for the investigation of possible stress cracking mechanisms; and welded coupons that are used to detect preferential corrosive action on weldments. 11.1.7 Hydrogen Probes Hydrogen probes are used to detect the penetration of elemental hydrogen into metal, pipe, and vessel. This can occur in cathodic reactions in acid solutions, particularly in the presence of hydrogen sulfide. There are three basic types of hydrogen probes. The simplest and most common consists of a thin-walled carbon steel tube inserted into the flow stream with a solid rod inside the tube forming a small annular space. Hydrogen atoms small enough to permeate the carbon steel collect in the annular space and combine to form molecular hydrogen gas that is too large to pass back into the process. As hydrogen gas collects, pressure builds in the annular space and registers on a pressure gauge located outside the piping. “Patch probes” operate identically except that the “patch” is sealed to the outside of the pipe or vessel and collects hydrogen atoms that penetrate the pipe wall. The third type of hydrogen probe is the palladium foil type that produces an electrical output proportional to hydrogen evolution rate. All three types of hydrogen probes provide useful information about changes in the corrosive environment in processes where HIC is present or could occur. If pressure is accumulating at a certain rate per day and then increases by a factor of 10, this indicates a significant change that should be addressed. Hydrogen probe readings, however, have not been found to be suitable for direct determination of corrosion rate, only of changes in the process, and it is recommend that they be applied carefully as part of a complete corrosion control program in applications where HIC is a concern. 11.1.8 Polarization Studies Polarization studies have been primarily laboratory electrochemical techniques to study corrosion phenomena, especially pitting, by disturbing the natural corrosion potential of a system, frequently by substantial amounts (a few volts compared with a few millivolts in linear polarization measurements) and measuring the external current flowing. With advances in computer technology, some of these systems are now being used in the field. In the laboratory, the metal/fluid environment can be carefully


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controlled. Such control is more difficult in the field, and the technique must be used more judicially there. A variety of methods and equipment are used for such studies that are generally classified under the following types: Potentiostatic

Potential held constant

Galvanostatic

Current held constant

Potentiodynamic (a) Potential changed continuously at a specified rate (b) Potential changed in steps and held constant at each step Galvanodynamic (a) Current changed continuously at a specified rate (b) Current changed in steps and held constant at each step (galvano staircase) The potentials or currents applied with these techniques may make irreversible changes to the metal-fluid interface because they may substantially polarize the metal away from its natural state in the fluid environment, generally preventing reuse of the test electrodes after one scan. In common with all electrochemical methods, they can only be made in sufficiently conductive media where the wetted electrode area is known. Although corrosion rates can be estimated with this technique, it tends to be less precise than linear polarization resistance (LPR) because of the high polarization potentials required.

11.1.9 Electrical Impedance Spectroscopy Electrochemical impedance spectroscopy (AC impedance) is a now wellestablished laboratory technique used to determine the electrical impedance of the metal–electrolyte interface at various AC excitation frequencies. Impedance measurements combine the effects of DC resistance with capacitance and inductance. In order to make impedance measurements, it is necessary to have a corrosion cell of known geometry, a reference electrode, and instrumentation capable of measuring and recording the electrical response of the test corrosion cell over a wide rate of AC excitation frequencies. Again, with the evolution of more rugged computers, some investigation of this method is now being made in the field. AC impedance is capable of characterizing the corrosion interface more comprehensively and with good quality equipment specifications of achieving measurements in lower conductivity solution or high-resistivity coatings. AC impedance measurements can be used to predict corrosion rates and characterize systems under study, and they are commonly used for performance studies of chemical inhibitors and protective coatings to evaluate the resistance of alloys to specific environments, etc.



539

11.1.10 Electrochemical Noise Electrochemical noise is a monitoring technique that directly measures naturally occurring electrochemical potential and current disturbances because of ongoing corrosion activity. It has the same media conductivity limitations and requirement for a known electrode area as the other electrochemical techniques. It is generally less quantitative than LPR for corrosion rate calculations, and it is more useful in detection of transient effects in marginally conductive situations. Laboratory and field interpretation is still rather developmental. Its proponents claim this technique can provide a large quantity of information that can be useful in determining what is actually happening in real time with corrosion activity in the piping or equipment being monitored. Detractors contend that there is, in fact, too much information and especially analyze when there is a contact but acceptable level of corrosion activity in the system or another source of potential electrical disturbance in the system. This technique may have merit as part of an on-site corrosion survey conducted by specialists trained to interpret the data, but by no means is it recommended as a permanent monitor or a substitute for other techniques. The CORRATERw instruments operating in the “pitting index” or “imbalance” mode provide a simple electrochemical current noise sample that is useful as an indicator of pitting tendency or surface instability. 11.1.11 Electrical Resistance Electrical resistance (ER) probes and instruments are basically “automatic coupons” and share many characteristics with coupons, as discussed above, when it comes to advantages and limitations. ER systems work by measuring the ER of a thin metal probe. As corrosion causes metal to be removed from the probe, its resistance increases. The major advantage of the ER method compared to coupons is that measurements can be obtained on a far more frequent basis and require much less effort to make. With automated systems, continuous readings are, in fact, made, and sophisticated data analysis techniques are now available that permit the detection of significant changes in corrosion rate in as little as 2 h without generating nuisance alarms. 11.1.12 CORROSOMETERw Systems CORROSOMETER (ER) monitoring systems can be applied to all processes. CORROSOMETER (ER) probe elements are available in a variety of styles. A selection of the available styles is shown in Figure 11.1. Wire loop, tube loop, and strip loop styles all have a loop of metal exposed to the process. The loop protrudes from the end of the probe body through either a hermetic glass seal or a Teflon/ceramic, Teflon/epoxy, or epoxy seal/packing system.


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Strip loop

Tube loop

Wire loop

Cylindrical

Atmospheric

Flush end view Flush end view

FIGURE 11.1 Selection of available CORROSOMETER probe element styles.

Choice of materials is dependent on stream composition, process conditions, and performance requirements. Cylindrical elements utilize specially made, thin wall tubing as the measurement element. Cylindrical probes are generally “all metal,” i.e., there is no other material exposed to the process. There are, however, some cylindrical probes available that join the probe body at a hermetic glass seal. Avariety offlush-mounted probes are also available, so called because the measuring element is mounted parallel to the flow stream, flush with the inside pipe wall. Some types of CORROSOMETER (ER) probes are better suited to the requirements of particular applications than others. Where pitting or substantial iron sulfide (FexSy) deposition are expected to be problems, cylindrical probes should be chosen over loop style probes if possible. It is possible that wire loop and tube loop elements may be severed by a pitting attack, necessitating probe replacement. Wire loop and tube loop elements also have a tendency to be electrically shorted by a bridge of iron sulfide corrosion product. This is especially prevalent in low-velocity streams over an extended period. The effect of such bridging is to reduce the measured metal loss of the probe, creating a misleadingly low corrosion rate. Cylindrical elements, on the other hand, are affected to a much lesser degree by pitting because of the much larger circumference of the measuring element. Cylindrical probes also demonstrate more resistance to iron-sulfide bridging because of their construction and lower inherent resistance per unit length, thus, minimizing the effect of the shunt resistance. Most cylindrical probes are of all-welded construction in order to eliminate the need for sealing metal elements to nonmetallic glass, epoxy, or ceramic. This all-welded construction gives the probe superior resistance to leaking. Probes with higher temperature ratings can also be constructed in the all-welded style. A drawback to the all-welded style is that the element is electrically connected to the pipe wall that can, under certain conditions, interfere with the corrosion reaction on the probe. Also, because cylindrical probes are welded, under some conditions, preferential corrosion can occur in the heat-affected zones near the weld or end grain attack can occur. Flush probe elements are thin, flat metal sections embedded in epoxy or a hermetic glass seal inside a metal probe body. Flush probes also experience certain characteristic problems, most notably lack of adhesion of the metal



541

element to the epoxy; cracking of glass seals because of differential expansion in changing temperature environments; and erosion of the epoxy or glass because of high velocities, abrasive materials in the flowstream, or both. Flush ER probes mounted on the bottom of the line have been shown to provide good results in a sour gas–gathering system. Because the measurement element is part of the primary pressure seal and because it is designed to corrode, ER probes have a reduced resistance to leaking after prolonged exposure. Once the measurement element has corroded through, the internals of the probe body are exposed to the process fluid. Although materials are chosen in part for their strength and lack of permeability, experience shows that process fluids will permeate throughout the probe packing materials. For this reason, quality probes are constructed of corrosion-resistant body materials and include an outboard pressure seal, often consisting of a hermetic glass-sealed connector. Other sealing materials are utilized in special cases, especially where process fluids will attack glass (e.g., hydrofluoric acid service), and secondary seals are also used in some probes, particularly when highly dangerous or toxic fluids are to be contained. The reference/check elements are protected from the process that the measurement element is directly exposed to. Because of the very low resistances involved, these changes can significantly affect the metal loss. Temperature changes in the process will, therefore, affect the measure element before the reference and check element readings. ER probes incorporate special design features to minimize the thermal resistance of the materials, insulating the reference and check elements from the process. It should also be noted that cylindrical probes are inherently better able to react to temperature changes because of location of the reference and check elements concentrically inside the measure element.

11.1.13 Linear Polarization Resistance LPR is an electrochemical technique that measures the DC current (imeas) through the metal–fluid interface that results from polarization of one or two electrodes of the material under study by application of a small electrical potential. Because imeas is related to icorr by a factor based on the anodic and cathodic Tafel slopes that are relatively constant for a given metal–fluid system, and because icorr is directly proportional to corrosion rate, LPR techniques result in instantaneous corrosion rate readings. This is a significant advantage over ER or coupon monitoring in that a series of readings, over a period of time, is required to determine corrosion rate. LPR measurements cannot, however, be made in nonconductive fluids or fluids that contain compounds that coat the electrodes (e.g., crude oil). LPR techniques are, therefore, used most commonly in industrial water systems.


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11.1.14 CORRATER Systems CORRATER systems measure the instantaneous corrosion rate of a metal in a conductive fluid using the LPR measurement technique. As described earlier, corrosion is an electrochemical process where electrons are transferred between anodic and cathodic areas on the corroding metal resulting in oxidation (corrosion) of the metal at the anode and reduction of cations in the fluid at the cathode. Sterns and Geary originally demonstrated that the application of a small polarizing potential difference (DE) from the corrosion potential (Ecorr) of a corroding electrode resulted in a measured current density (imeas) that is related to the corrosion current density (icorr) by Equation 11.1:

where

DE ba bc Z ; imeas ð2; 303 icorr Þðba C bc Þ

(11.1)

baZanodic Tafel slope bcZcathodic Tafel slope. Because the Tafel coefficients are more or less constant for a given metal– fluid combination, imeas is proportional to icorr that is proportional to the corrosion rate. Equation 11.1 and the entire LPR technique are only valid when the polarizing potential difference is very low (typically up to 20 mV). In this region, the curves are linear, hence the term LPR. Inspection of Equation 11.1 shows that the result is a resistance, the polarization resistance, Rp. Strictly speaking, there are both anodic and cathodic Rp values that can differ, they are usually assumed to be equal. The resistance to current flow between anode and cathode on the LPR probe is the sum of both polarization resistance values and the resistance of the solution between the electrodes (Rs) as shown in Equation 11.2: DE Z imeas ð2Rp C Rs Þ

(11.2)

From Equation 11.1 and Equation 11.2, obtaining results from the LPR technique would seem to require only instantaneous readings of resistance. In practice, however, the determination of polarization resistance is complicated by a capacitance effect at the metal–fluid interface (doublelayer capacitance). Figure 11.2 is an equivalent electrical circuit of the corrosion cell formed by the measuring electrodes and the fluid, showing the importance of Rs and double-layer capacitance effects. The effect of the double-layer capacitance is to require the direct current flow to initially charge up the capacitors, resulting in a decaying exponential current flow curve vs. time, after application of the polarizing potential difference. A typical LPR current vs. time curve is shown in Figure 11.3. Each metal– fluid interface has its own characteristic capacitance that in turn, determines the amount of time required to obtain valid measurements of icorr and



543 RP

RP RS

Test electrode

Cdl

Cdl Auxiliary electrode Reference electrode (where used)

FIGURE 11.2 Equivalent circuit of LPR probe.

Applied potential and resultant current

corrosion rate. The actual time required can vary from a few seconds up to 20 min, depending on the metal–process combination being measured. Choosing too short a polarization time can result in current readings much higher than the true icorr, thus, causing measured corrosion rate to be lower than actual, sometimes by a significant amount. Solution resistance can also have a significant effect on accuracy if it is relatively high compared to the polarization resistance. In most industrial water applications, conductivity of the solution is high and solution resistance is low compared to the polarization resistance, so imeas is an accurate measure of polarization resistance and, therefore, corrosion rate.

Resultant current Applied voltage step (typically 10 mv) imeas

Time

Current asymptote (D.C. component of current)

FIGURE 11.3 Type LPR current vs. time decay curve.


544


high purity distilled water

good quality distilled water

rain water

good quality drinking water

normal range of cooling waters

sea water

mils per year

mm per year

A serious problem develops, however, when the solution resistance increases or the polarization resistance decreases enough to make the solution resistance a significant portion of the total resistance to current flow between the electrodes. In these cases, the accuracy of the LPR measurement is affected. This situation tends to occur at high corrosion rates (low polarization resistance) and in solutions with low conductivity (high solution resistance) and is manifested by the indicated (measured) corrosion rate being lower than the actual corrosion rate. The graph in Figure 11.4 shows the effect of this limitation on the recommended operating range of LPR instruments. Several techniques have been used over the years to minimize the impact of solution resistance on LPR measurements. The most common technique involved the use of a three-electrode probe. The effectiveness of the reference electrode in reducing the effect of solution resistance has been shown to be dependent on the proximity of the reference electrode to the measurement electrode.

10,000 Typical corrosion rate of carbon steel

100 1000 Non-operating region

10 100 1 10 Operating region

0.1

1 2

1

3

0.01 0.1 100K

10K

1K

100

10

1

0.1

Conductivity (μmhos/cm) 1 2 3

2 electrode probes with Model AQUAMATETM, 9030, AQUACORR®, CORRDATA®, RCS8, and 9134 instruments 2 electrode probes on Model 9000 and SCA-1 with conductivity correction 2 electrode probes on Model 9000 and SCA-1 with conductivity correction

NOTES: 1. Operating range limits based on nominal 20% error in measurement of RP. 2. For copper alloys, typical corrosion rate of carbon steel is increased by alloy multiplier.

FIGURE 11.4 Operating range of LPR instruments: corrosion rate vs. solution conductions.



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A better way to deal with this problem, however, is to directly measure and compensate for the solution resistance. In this method, a high-frequency AC voltage signal is applied between the electrodes short-circuiting Rp through the double-layer capacitance, thereby, directly measuring the solution resistance. The state-of-the-art, patented SRC technology also eliminates the need for a third electrode, even in low-conductivity solutions. Consequently, the two-electrode probes have become the standard with the three-electrode probe available on special order only. The above points are clearly indicated in ASTM Standard Guide G96 that states: 3.2.8 Two-electrode probes and three-electrode probes with the reference electrode equidistant from the test and auxiliary electrode do not correct for effects of solution resistance without special electronic solution resistance compensation. With high to moderate conductivity environments, this effect of solution resistance is not normally significant. 3.2.9 Three-electrode probes compensate for the solution resistance Rs by varying degrees depending on the position and proximity of the reference electrode to the test electrode. With a close-spaced reference electrode, the effects of Rs can be reduced up to approximately ten-fold. This extends the operating range over that adequate determination of the polarization resistance can be made. 3.2.10 A two-electrode probe with electrochemical impedance measurement technique at high frequency short circuits the double-layer capacitance. Cdl, so that a measurement of solution resistance Rs can be made for application as a correction. This also extends the operating range over which adequate determination of polarization resistance can be made.

11.2 Comparison of CORROSOMETER (ER) and CORRATER (LPR) Measurement Techniques The CORROSOMETER (ER) and CORRATER (LPR) techniques are both extremely effective corrosion monitoring methods. The choice of which is better is dependent on the application. The principal attributes and limitations of each are briefly summarized below: 1. CORRATER systems require a sufficiently conductive liquid; CORROSOMETER systems are suitable for all environments. 2. CORROSOMETER systems measure metal loss directly, and their accuracy is comparable to the coupon method. CORRATER systems determine corrosion rate based on electrochemical theory and depend on average calibration constants to determine corrosion rate.


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3. CORRATER systems measure corrosion rate virtually instantaneously. CORROSOMETER systems measure metal loss so that corrosion rate must be determined over a period of time, usually a few hours to a few days. 4. CORRATER systems supply pitting tendency information; CORROSOMETER systems do not at this time.

11.3 Applications Suited to CORRATER (LPR) and CORROSOMETER (ER) Techniques Because of their intrinsic properties, CORRATER and CORROSOMETER systems are generally used in different applications. Occasionally, both are used to obtain complementary information; however, application requirements will usually dictate the choice of one or the other. The following are the principal uses of and applications for CORRATER products: 1. Control of inhibitor addition in water systems a. For control of injection to minimize corrosion rises b. Evaluate different inhibitors and optimize their effectiveness over time 2. Evaluation and prescreening of inhibitors in the laboratory before field trials 3. Cooling towers—to optimize inhibition control, detect process leakage or oxygen activity and microbiologically-induced corrosion effects on the alloys of construction 4. Oil field waterfloods—to protect the injection equipment, particularly from oxygen ingress 5. Oil field drilling mud—to control inhibitor additions 6. Geothermal systems—to monitor the condition of produced brine and changes occurring before reinjection 7. Desalination systems—to monitor water quality 8. Process waters, scrubbers—to detect particularly corrosive contaminants 9. Evaluation of various alloys to solve material selection options, particularly in pilot or full-scale plant environments 10. Potable water systems—to test effectiveness of inhibitors and corrosiveness of biocides The CORROSOMETER has much broader application and can be used in any medium, specifically



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1. In oil and gas production 2. In gas sweetening, storage, and transportation systems 3. In refineries and petrochemical plants 4. In inhibitor evaluation/optimization programs 5. In power plants—for cooling water, feedwater, and scrubber systems. In bag houses and stacks for special function such as dew point alarming in flue gas systems 6. In chemical processes 7. In cathodically protected systems 8. In air-cleaning systems in control rooms 9. In paper mills or other plants with a volatile inherently corrosive process stream


Index

A Absorption, 292–293, 380, 385 Acrylic paints, 488–489 Adhesion of paint film, 477–478 Adsorption, 55, 60–61 Alkyd resin paints, 493–494 Aluminum anodes, 48 Anodic undermining, 480 Anodized coatings, 457–459 Auxiliary anodes, 50–51

B Bisphenol A fumurate polyester linings, 159–164 Buna N, see nitrile rubber sheet linings Butyl rubber sheet linings, 310, 315–318

C Cathodic delamination, 480 Cathodic sputtering, 419–420 Cement coatings, 509–513 Chemical analysis, 535–536 Chemisorption, 55, 61–62 Chlorinated polyvinyl chloride sheet linings, 345, 354–357 Chlorinated rubber paints, 488 Chlorobutyl rubber sheet lining, 325, 331–332 Chlorosulfonated polyethylene, see Hypalon Chlorosulfonated polyethylene sheet lining, 110, 111, 117–120, 314, 318–322 Chlorotrifluoroethylene, 134, 138, 143–146 Chlorotrifluoroethylene sheet lining, 386, 390, 394–398 Chromate coating, 455–457 Chromium coatings, 427–429 Coupon teste, 536–537

D Destructive analysis, 535 Diffusion coating, 420

Duplex nickel coatings, 424–425

E ECTFE, see Halar, chlorotrifluoroethylene sheet lining EHMWPE, see polyethylene sheet lining Elastomeric sheet linings, 295–342 Electrical impedance spectroscopy, 558 Electrical resistance, 539 Electrochemical noise, 539 Electroless plating, 418 Electrophoretic deposition, 418–419 Electroplating, 417–418 Environmental stress cracking, 293 EPDM, see ethylene propylene sheet lining Epoxy ester paints, 493 Epoxy mortars and grouts, 4–7 Epoxy paints, 490–491 ETFE, see Tefzel, ethylene tetrafluoroethylene sheet lining Ethylene propylene rubber sheet lining, 328, 331–356 Ethylene tetrafluoroethylene, 386, 390–394 Explosive bonding, 421 Extenders, see fillers

F FEP, see fluorinated ethylene propylene sheet lining Filiform corrosion, 481–482 Fillers (of organic coatings), 468–471 FKM, see fluoroelastomers Flame and plasma spraying, 420 Fluoroelastomer rubber sheet lining, 336, 338–343 Fluorinated ethylene propylene linings, 121, 125, 130–133, 367, 379–388 Food container coatings, 429–431 Furan mortars and grouts, 7–9 Fluoroelastomer linings, 142, 146–151 Fusion bonding, 421

549

CAT8247—Index—6/10/2006—12:58—SRIDHAR—XML MODEL B – pp. 549–551

550

G Galfan, 448–451 Galvalume coatings, 438, 448–451 Gas plating, 421 Gold coatings, 432 Grouts, 3–16 inorganic, 13 organic, 3–13

H Halar, 134, 138, 143–146 Halar sheet linings, see chlorotrifluoroethylene sheet linings Halogenated polyester linings, 164, 167–171 HMWPE, see polyethylene sheet linings Hot dipping, 420 Hydrogen probes, 537 Hydrogenated Bisphenol A fumurate polyester linings, 165–167 Hypalon, 110, 111, 117–120 Hypalon sheet lining, see chlorosulfonated polyethylene sheet lining

I Inhibitor classification, 57–59 organic, 58–59 passivation, 57–58 precipitation, 59 Inhibitor efficiency, 62–63 Isophthalic polyester linings, 147, 151, 155–159 Isoprene, 306

K Kynar, see polyvinylidene fluoride

L Lead coatings, 431–432 Linear polorization resistance, 541 Lining, coal tar, 97, 102–103, 106–107 Lining, coal tar epoxy, 97, 104–105 Linings, epoxy, 85–92 Lining, epoxy polyamide, 93, 102–103 Lining, furan, 88–97 Linings, neoprene, 107, 109–114 Linings, phenolic, 84–85, 87 Linings, plastisol, 116, 120–125 Linings, polysulfide rubber, 110, 115–116 Linings, urethans, 103, 105, 108–109 Linings, vinyl ester, 93, 98–101

Corrosion of Linings and Coatings Liquid applied linings, compatibility of with selected corrodents (table), 175–286

M Manganese coatings, 452 Magnesium anodes, 48–50 Metal cladding, 421 Microcracked chromium coatings, 428 Nonnoble coatings, 435–440 Monolithic surfacings, 2, 16–42 chemical resistance of, 37–40 Mortars, 2–16 corrosion resistance of, 17–34 inorganic, 13 organic, 3–13

N Natural rubber, 296–309 NBR, see nitrile rubber sheet linings Neoprene sheet linings, 309–314 Nickel coatings, 423–426 Nickel-iron alloy coatings, 426–427 Nitrile rubber sheet linings, 356–358 Noble coatings, 421–423

O Organic coatings, 459–469 composition of, 461–469 Oxide coatings, 457

P Paint, 487–501 Paints, composition of, 461–471 additives, 469 fillers, 468–471 pigment, 467–468 resin, 461–467 solvent, 469–470 Paint failure, causes of, 482–484 Paint film deterioration, 476–477 Paint selection, 496–499 Perfluoroalkoxy linings, 121, 126–129 sheet linings, 385–386, 390 Permeation, 290–292, 375, 380, 385 PFA, see perfluoroalkoxy Phenolic coatings (linings), 84–85 Phenolic mortar and grout, 9–10 Phosphate coating, 454–455 Pigment component (of organic coating), 467–468


Index Polarization studies, 537–538 Polyester elastomer sheet lining, 322, 325, 326, 329–330 Polyester mortars and grouts, 10–12 Polyethylene sheet lining, 362, 367–375 Polypropylene sheet lining, 353, 357, 363–366 Polyvinyl chloride sheet lining, 345–353 Polyvinylidene chloride sheet lining, 398–402 Polyvinylidene fluoride linings, 147, 152–155 Polyvinylidene fluoride sheet linings, 345, 353, 358–361 Portland cement coatings, 512–513 PTFE linings, 125, 129, 134–138 PTFE sheet linings, see tetrafluoroethylene sheet linings PVC sheet lining, see polyvinyl chloride sheet lining PVDF, see polyvinylidene fluoride PVDF sheet lining, see polyvinylidene sheet lining

R

551 environmental stress cracking, 293 permeation, 290–292 Sheet linings, cause of failure, 294–295 High temperature protective oxides, see protective oxides (high temperature) Silicate cement coatings, 510–512 Silicate mortars, 15–16 Silicone linings, 171–174 Silicone paints, 494–495 Solef, see polyvinylidene fluoride Sulfur mortars, 14–15

T Teflon, see PTFE Tefzel linings, 134, 139–192 Terneplate, 432 Tetrafluoroethylene sheet linings, 367, 375–379 Thermoplastic sheet linings, 393–402 Tin coatings, 429–431 Tinplate, 429–431 Trinickel, 424

Radiography, 524 Recommended paint systems based on environment acidic chemical exposure (pH 2.0–5.0), 506 exposure to mild solvents, 507 extreme pH exposure, 507 fresh water exposure, 503 fresh water immersion, 506 mild exposure, 499 neutral chemical exposure (pH 5.0–10.0), 506 normally dry interior, 499, 503 salt water exposure, 505 salt water immersion, 506–507 temporary protection, 499 Resin component (of organic coatings), 461–467

U

S

Water emulsion paints, 494

Sacrificial anode, 14, 47–51 Sacrificial metal coatings, 413, 436–440 Saran, see polyvinylidene chloride sheet linings Scrap iron anodes, 50–51 Sheet linings, 287–402 design considerations: absorption, 292–293

Z

Ultrasonic measurements, 534–535 Urethane paints, 491–492 Urethane rubber sheet linings, 318, 322–325

V Vacuum and vapor deposition, 420 Vehicle binder, see resin component Vinyl ester mortar and grouts, 12–13 Vinyl eater novolac mortars and grouts, 12–13 Vinyl ester paints, 492 Visual inspection, 535

W

Zaluite, see Galvalume coatings Zincalume, see Galvalume coatings Zinc, 15% aluminum thermal spray, 451 Zinc anodes, 48 Zinc-iron coatings, 451 Zinc rich paints, 495–496


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